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A115285

Diagonal sums of correlation triangle for 1,3,4,4,4,...(A113311).

1, 3, 7, 14, 23, 35, 50, 67, 87, 110, 135, 163, 194, 227, 263, 302, 343, 387, 434, 483, 535, 590, 647, 707, 770, 835, 903, 974, 1047, 1123, 1202, 1283, 1367, 1454, 1543, 1635, 1730, 1827, 1927, 2030, 2135, 2243, 2354, 2467, 2583, 2702, 2823, 2947, 3074

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OFFSET

0,2

COMMENTS

Diagonal sums of number triangle A115284.

LINKS

Table of n, a(n) for n=0..48.

Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).

FORMULA

G.f.: (1+x)^2*(1+x^2)^2/((1-x)*(1-x^2)*(1-x^3)).

a(n) = Sum_{k=0..floor(n/2)} Sum_{j=0..n-k} [j<=k]*(4-C(1, k-j)-2*C(0, k-j))*[j<=n-2*k]*(4-C(1, n-2*k-j)-2*C(0, n-2*k-j)).

MATHEMATICA