A027327 - OEIS

A027327

a(n) = Sum_{k=0..m} (k+1) * A026120(n, m-k), where m=0 for n=0,1; m=n for n >= 2.

1, 3, 12, 36, 108, 324, 972, 2916, 8748, 26244, 78732, 236196, 708588, 2125764, 6377292, 19131876, 57395628, 172186884, 516560652, 1549681956, 4649045868, 13947137604, 41841412812, 125524238436, 376572715308

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..24.

Index entries for linear recurrences with constant coefficients, signature (3).

FORMULA

G.f.: (1+3x^2)/(1-3x). - Paul Barry, May 19 2003

a(n) = A003946(n), n>1. - R. J. Mathar, Oct 23 2008

MATHEMATICA

Join[{1, 3}, NestList[3#&, 12, 30]] (* Harvey P. Dale, Aug 13 2024 *)

PROG

(PARI) a(n)=if(n>1, 4*3^n/3, 2*n+1) \\ Charles R Greathouse IV, May 29 2026

CROSSREFS

Cf. A026120, A003946.

Sequence in context: A167667 A292291 A215919 * A290927 A167993 A398039

Adjacent sequences: A027324 A027325 A027326 * A027328 A027329 A027330

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling

STATUS

approved