0,2

Coefficients for numerical differentiation.

Take the first n integers 1, 2, 3, ..., n and find all combinations with repetitions allowed for the first n of them. Find the sum of each of these combinations to get this sequence. Example for 1 and 2: 1, 2, 1+1, 1+2, 2+2 gives sum of 12 = a(2). - J. M. Bergot, Mar 08 2016

Let cos(x) = 1 -x^2/2 +x^4/4!-x^6/6!... = Sum_i (-1)^i x^(2i)/(2i)! be the standard power series of the cosine, and y = 2*(1-cos(x)) = 4*sin^2(x/2) = x^2 -x^4/12 +x^6/360 ... = Sum_i 2*(-1)^(i+1) x^(2i)/(2i)! be a closely related series. Then this sequence represents the reversion x^2 = Sum_i 1/a(i) *y^(i+1). - R. J. Mathar, May 03 2022

C. Lanczos, Applied Analysis. Prentice-Hall, Englewood Cliffs, NJ, 1956, p. 514.

J. Ser, Les Calculs Formels des Séries de Factorielles. Gauthier-Villars, Paris, 1933, p. 92.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

T. D. Noe, Table of n, a(n) for n=0..200

W. G. Bickley and J. C. P. Miller, Numerical differentiation near the limits of a difference table, Phil. Mag., 33 (1942), 1-12 (plus tables) [Annotated scanned copy]

Ömür Deveci and Anthony G. Shannon, Some aspects of Neyman triangles and Delannoy arrays, Mathematica Montisnigri (2021) Vol. L, 36-43.

C. Lanczos, Applied Analysis (Annotated scans of selected pages)

A. Petojevic and N. Dapic, The vAm(a,b,c;z) function, Preprint 2013.

H. E. Salzer, Coefficients for numerical differentiation with central differences, J. Math. Phys., 22 (1943), 115-135.

H. E. Salzer, Coefficients for numerical differentiation with central differences, J. Math. Phys., 22 (1943), 115-135. [Annotated scanned copy]

J. Ser, Les Calculs Formels des Séries de Factorielles, Gauthier-Villars, Paris, 1933 [Local copy].

J. Ser, Les Calculs Formels des Séries de Factorielles (Annotated scans of some selected pages)

R. Shenton and A. W. Kemp, An S-fraction and ln^2(1+x), Journal of Computational and Applied Mathematics, 26 (1989) 367-370 North-Holland.

T. R. Van Oppolzer, Lehrbuch zur Bahnbestimmung der Kometen und Planeten, Vol. 2, Engelmann, Leipzig, 1880, p. 21.

Mats Vermeeren, A dynamical solution to the Basel problem, arXiv preprint arXiv:1506.05288 [math.CA], 2015.

a(n) = A002736(n+1)/2.

G.f.: (1 + 2*x)/(1 - 4*x)^(5/2).

a(n-1) = Sum_(i_1 + i_2 + ... + i_n) where the sum is over 0 <= i_1 <= i_2 <= ... <= i_n <= n; a(n) = (n+1)^2 C(2n+1, n). - David Callan, Nov 20 2003

a(n) = (n+1)^2 * binomial(2*n+2,n+1)/2. - Zerinvary Lajos, May 31 2006

Asymptotics: a(n)-> (1/64) * (128*n^2+176*n+41) * 4^n * n^(-1/2)/(sqrt(Pi)), for n->infinity. - Karol A. Penson, Aug 05 2013

G.f.: 2F1(3/2,2;1;4x). - R. J. Mathar, Aug 09 2015

a(n) = A002457(n)*(n+1). - R. J. Mathar, Aug 09 2015

a(n) = A000217(n)*A000984(n). - J. M. Bergot, Mar 10 2016

a(n-1) = A001791(n)*n*(n+1)/2. - Anton Zakharov, Jul 04 2016

From Ilya Gutkovskiy, Jul 04 2016: (Start)

E.g.f.: ((1 + 2*x)*(1 + 8*x)*BesselI(0,2*x) + 2*x*(3 + 8*x)*BesselI(1,2*x))*exp(2*x).

Sum_{n>=0} 1/a(n) = Pi^2/9 = A100044. (End)

From Peter Bala, Apr 18 2017: (Start)

With x = y^2/(1 + y) we have log^2(1 + y) = Sum_{n >= 0} (-1)^n*x^(n+1)/a(n). See Shenton and Kemp.

Series reversion ( Sum_{n >= 0} (-1)^n*x^(n+1)/a(n) ) = Sum_{n >= 1} 2*x^n/(2*n)! = Sum_{n >= 1} x^n/A002674(n). (End)

D-finite with recurrence n^2*a(n) -2*(n+1)*(2*n+1)*a(n-1) = 0. - R. J. Mathar, Feb 08 2021

Sum_{n>=0} (-1)^n/a(n) = 4*arcsinh(1/2)^2 = A202543^2. - Amiram Eldar, May 14 2022

seq((n+1)^2*(binomial(2*n+2, n+1))/2, n=0..29); # Zerinvary Lajos, May 31 2006

Table[Binomial[2n+1, n](n+1)^2, {n, 0, 20}] (* Harvey P. Dale, Mar 23 2011 *)

(PARI) a(n)=binomial(2*n+1, n)*(n+1)^2

(PARI) x='x+O('x^99); Vec((1+2*x)/(1-4*x)^(5/2)) \\ Altug Alkan, Jul 09 2016

(Python)

from sympy import binomial

def a(n): return binomial(2*n + 1, n)*(n + 1)**2 # Indranil Ghosh, Apr 18 2017

(Magma)

A002544:= func< n | (n+1)^2*Binomial(2*n+2, n+1)/2 >;

[A002544(n): n in [0..30]]; // G. C. Greubel, Nov 17 2025

(SageMath)

def A002544(n): return (n+1)^2*binomial(2*n+2, n+1)//2

print([A002544(n) for n in range(31)]) # G. C. Greubel, Nov 17 2025

Cf. A000217, A000984, A001791, A002457, A002674, A002736, A085373, A202543.

A diagonal of A331430.

Sequence in context: A022640 A090749 A130592 * A093801 A273099 A249979

Adjacent sequences: A002541 A002542 A002543 * A002545 A002546 A002547

nonn,easy,nice

N. J. A. Sloane, Simon Plouffe

approved