A371441 - OEIS

A371441

a(n) = a(n-1)*3^n + 1 where a(0)=1.

1, 4, 37, 1000, 81001, 19683244, 14349084877, 31381448626000, 205893684435186001, 4052605390737766057684, 239302295717674347940182517, 42391683779498857714559512339000, 22528678819460652442683221796950499001, 35917990801478965784376042224979510418771324

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..13.

FORMULA

a(n) = Sum_{k=0..n} 3^(k*(2*n + 1 - k)/2). - Vaclav Kotesovec, Apr 10 2024

MATHEMATICA

Table[Sum[3^(k*(2*n + 1 - k)/2), {k, 0, n}], {n, 0, 15}] (* Vaclav Kotesovec, Apr 10 2024 *)

Block[{n = 0}, NestList[#*3^++n + 1 &, 1, 15]] (* Paolo Xausa, Apr 19 2024 *)

PROG

(Python)