A036542 a(n) = T(n, n), array T given by A047858.

1, 3, 11, 34, 93, 236, 571, 1338, 3065, 6904, 15351, 33782, 73717, 159732, 344051, 737266, 1572849, 3342320, 7077871, 14942190, 31457261, 66060268, 138412011, 289406954, 603979753, 1258291176, 2617245671, 5435817958, 11274289125, 23353884644, 48318382051

Offset: 0

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Colin Barker, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (6,-13,12,-4).

Programs

Mathematica

LinearRecurrence[{6,-13,12,-4},{1,3,11,34},40] (* Harvey P. Dale, Jul 21 2024 *)

PARI

Vec((1-3*x+6*x^2-5*x^3)/((1-x)^2*(1-2*x)^2) + O(x^40)) \\ Colin Barker, Feb 20 2016

Formula

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

From Colin Barker, Feb 20 2016: (Start)

a(n) = 6*a(n-1)-13*a(n-2)+12*a(n-3)-4*a(n-4) for n>3.

G.f.: (1-3*x+6*x^2-5*x^3) / ((1-x)^2*(1-2*x)^2).

(End)