A392266 a(n) = (3^n + 2*n*3^(n-1) - 1)/4.

0, 1, 5, 20, 74, 263, 911, 3098, 10388, 34445, 113177, 369056, 1195742, 3852947, 12356003, 39459494, 125552936, 398182169, 1259116589, 3971060012, 12494310770, 39226324511, 122909150135, 384417980210, 1200325530044, 3742191358373, 11650218379841, 36221588053688, 112477562903558, 348871084938155

Offset

0,3

Links

Table of n, a(n) for n=0..29.

Formula

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

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

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

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

Crossrefs

First differences of A261064.

Cf. A006234.

Sequence in context: A006650 A034535 A316222 * A273718 A094806 A289596

Adjacent sequences: A392263 A392264 A392265 * A392267 A392268 A392269

Keyword

nonn,easy

Author

Enrique Navarrete, Jan 05 2026

Status

approved