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A045803

3-ish numbers (end in 17, 19, 31, 33).

17, 19, 31, 33, 117, 119, 131, 133, 217, 219, 231, 233, 317, 319, 331, 333, 417, 419, 431, 433, 517, 519, 531, 533, 617, 619, 631, 633, 717, 719, 731, 733, 817, 819, 831, 833, 917, 919, 931, 933, 1017, 1019, 1031, 1033, 1117, 1119, 1131, 1133, 1217, 1219

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OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).

FORMULA

G.f.: x*(17+2*x+12*x^2+2*x^3+67*x^4)/(1-x-x^4+x^5). - Colin Barker, Jan 23 2012

a(n) = -75/2 - (23*(-1)^n)/2 - (9-9*i)*(-i)^n - (9+9*i)*i^n + 25*n where i=sqrt(-1). - Colin Barker, Oct 16 2015

MATHEMATICA

Select[Range[1300], MemberQ[{17, 19, 31, 33}, Mod[#, 100]]&] (* or *) LinearRecurrence[{1, 0, 0, 1, -1}, {17, 19, 31, 33, 117}, 50] (* Harvey P. Dale, Dec 17 2014 *)

PROG

(Haskell)

import Data.List (findIndices)

a045803 n = a045803_list !! (n-1)

a045803_list = findIndices (`elem` [17, 19, 31, 33]) $ cycle [0..99]

-- Reinhard Zumkeller, Jan 23 2012

(PARI) a(n) = -75/2 - (23*(-1)^n)/2 - (9-9*I)*(-I)^n - (9+9*I)*I^n + 25*n \\ Colin Barker, Oct 16 2015

(PARI) Vec(x*(17+2*x+12*x^2+2*x^3+67*x^4)/(1-x-x^4+x^5) + O(x^100)) \\ Colin Barker, Oct 16 2015

CROSSREFS

Cf. A045800-A045809.

Cf. A045572, A045797, A045798.

Sequence in context: A155089 A101396 A050266 * A098933 A145485 A290634