A024392 a(n) = 3rd elementary symmetric function of the first n+2 positive integers congruent to 2 mod 3.

80, 806, 4040, 14155, 39655, 95200, 204036, 400830, 734910, 1273910, 2107820, 3353441, 5159245, 7710640, 11235640, 16010940, 22368396, 30701910, 41474720, 55227095, 72584435, 94265776, 121092700, 153998650, 194038650, 242399430

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).

Formula

a(n) = n*(n+1)*(n+2)*(3*n+7)*(9*n^2+33*n+22)/48.

G.f.: -x*(80+246*x+78*x^2+x^3) / (x-1)^7 . - R. J. Mathar, Oct 08 2011

Mathematica

Table[n (n + 1) (n + 2) (3 n + 7) (9 n^2 + 33 n + 22) / 48, {n, 1, 50}] (* Vincenzo Librandi, Jul 07 2019 *)

Prog

(Magma) [n*(n+1)*(n+2)*(3*n+7)*(9*n^2+33*n+22)/48: n in [1..40]]; // Vincenzo Librandi, Jul 07 2019

Crossrefs

Sequence in context: A164753 A279745 A062911 * A200550 A052519 A246545

Adjacent sequences: A024389 A024390 A024391 * A024393 A024394 A024395

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved