A176777 - OEIS

A176777

a(n) = 2^n - n*(n-3).

1, 4, 6, 8, 12, 22, 46, 100, 216, 458, 954, 1960, 3988, 8062, 16230, 32588, 65328, 130834, 261874, 523984, 1048236, 2096774, 4193886, 8388148, 16776712, 33553882, 67108266, 134217080, 268434756, 536870158, 1073741014, 2147482780, 4294966368, 8589933602, 17179868130, 34359737248

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Table of n, a(n) for n=0..35.

Index entries for linear recurrences with constant coefficients, signature (5,-9,7,-2).

FORMULA

a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4).

G.f.: (1-x-5*x^2+7*x^3)/((2*x-1)*(x-1)^3).

E.g.f.: exp(x)*(x*(2 - x) + exp(x)). - Elmo R. Oliveira, Apr 03 2025

MATHEMATICA

Table[2^n-n*(n-3), {n, 0, 5!}]