A061983 - OEIS

%I #10 Dec 29 2024 00:41:57

%S 0,0,1,11,54,202,671,2109,6460,19556,58893,176959,531218,1594062,

%T 4782667,14348561,43046328,129139720,387419993,1162260915,3486783790,

%U 10460352530,31381058871,94143178021,282429535604,847288608492,2541865827301,7625597483879,22876792453770

%N a(n) = 3^n - (3*n^2 + n + 2)/2.

%H Harry J. Smith, <a href="/A061983/b061983.txt">Table of n, a(n) for n = 0..200</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,10,-3).

%F G.f.: x^2*(1 + 5*x)/((1 - x)^3*(1 - 3*x)). - _Andrew Howroyd_, Dec 28 2024

%o (PARI) a(n) = { 3^n - (3*n^2 + n + 2)/2 } \\ _Harry J. Smith_, Jul 29 2009

%Y Column of A061980.

%K nonn

%O 0,4

%A _Henry Bottomley_, May 24 2001