A392266 - OEIS

%I #8 Jan 09 2026 16:30:16

%S 0,1,5,20,74,263,911,3098,10388,34445,113177,369056,1195742,3852947,

%T 12356003,39459494,125552936,398182169,1259116589,3971060012,

%U 12494310770,39226324511,122909150135,384417980210,1200325530044,3742191358373,11650218379841,36221588053688,112477562903558,348871084938155

%N a(n) = (3^n + 2*n*3^(n-1) - 1)/4.

%F a(n) = (3^n + 2*n*3^(n-1) - 1)/4.

%F a(n) = Sum_{k=3..n+2} A006234(k).

%F G.f.: x*(1 - 2*x)/((1 - x)*(1 - 3*x)^2).

%F E.g.f.: (1/4)*exp(x)*(exp(2*x)*(2*x + 1) - 1).

%Y First differences of A261064.

%Y Cf. A006234.

%K nonn,easy

%O 0,3

%A _Enrique Navarrete_, Jan 05 2026