A140431 a(n) = 2*A094555(n).

0, 2, 2, 12, 22, 92, 222, 772, 2102, 6732, 19342, 59732, 175782, 534172, 1588862, 4793892, 14327062, 43090412, 129052782, 387595252, 1161911942, 3487483452, 10458955102, 31383855812, 94137586422, 282440721292, 847266239822, 2541910567572, 7625508006502, 22876971411932

Offset

0,2

Links

Stefano Spezia, Table of n, a(n) for n = 0..2000

Index entries for linear recurrences with constant coefficients, signature (2,5,-6).

Formula

b(n) = A091002(n-1); b(n+1)-3b(n) = A077925(n-2), where b(n) = floor(a(n)/10).

From Colin Barker, Sep 21 2012; (Start)

a(n) = (1-(-2)^n+3^n)/3 for n>0. a(n) = 2*a(n-1)+5*a(n-2)-6*a(n-3) for n>3.

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

E.g.f.: exp(-2*x)*(exp(5*x) + exp(3*x) - exp(2*x) - 1)/3. - Stefano Spezia, Oct 05 2025

Mathematica

LinearRecurrence[{2, 5, -6}, {0, 2, 2, 12}, 30] (* Stefano Spezia, Oct 05 2025 *)

Crossrefs

Cf. A077925, A091002, A094555.

Sequence in context: A346757 A202669 A178845 * A092900 A303537 A369086

Adjacent sequences: A140428 A140429 A140430 * A140432 A140433 A140434

Keyword

nonn,walk,easy

Author

Paul Curtz, Jun 19 2008

Extensions

Edited and extended by R. J. Mathar, Aug 02 2008

a(27)-a(29) from Stefano Spezia, Oct 05 2025

Status

approved