A036551 a(n) = 2^(n-1)*(3^n-1) + 1.

1, 3, 17, 105, 641, 3873, 23297, 139905, 839681, 5038593, 30232577, 181397505, 1088389121, 6530342913, 39182073857, 235092475905, 1410554920961, 8463329656833, 50779978203137, 304679869743105, 1828079219507201, 10968475319140353, 65810851919036417

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 (9,-20,12).

Crossrefs

Cf. A048471.

Programs

PARI

Vec((1-6*x+10*x^2)/((1-x)*(1-2*x)*(1-6*x)) + O(x^30)) \\ Colin Barker, Aug 24 2016

Formula

a(n) = T(n, n), array T given by A048471.

From Colin Barker, Aug 24 2016: (Start)

a(n) = 9*a(n-1)-20*a(n-2)+12*a(n-3) for n>2.

G.f.: (1-6*x+10*x^2) / ((1-x)*(1-2*x)*(1-6*x)).

(End)

Extensions

Simpler definition from Ralf Stephan, Feb 17 2004

Corrected by T. D. Noe, Nov 07 2006