A126946 The sequence b[n] defined in A126940.

0, 2, 4, 12, 40, 128, 404, 1282, 4076, 12946, 41110, 130570, 414708, 1317126, 4183250, 13286248, 42197850, 134022604, 425663006, 1351928684, 4293798244, 13637334278, 43312907878, 137564127106, 436911072754, 1387653086532, 4407260902428, 13997697874880

Offset

0,2

Comments

Linear recurrence and empirical g.f confirmed for more terms. - Ray Chandler, Mar 07 2024

Links

Ray Chandler, Table of n, a(n) for n = 0..1993

Index entries for linear recurrences with constant coefficients, signature (2, 1, 7, 4, 4, 1).

Formula

Empirical g.f.: 2*x*(x^3-x^2-1) / (x^6+4*x^5+4*x^4+7*x^3+x^2+2*x-1). - Colin Barker, Apr 08 2013

Prog

(PARI) a(n)=([0, 1, 0, 0, 0, 0; 0, 0, 1, 0, 0, 0; 0, 0, 0, 1, 0, 0; 0, 0, 0, 0, 1, 0; 0, 0, 0, 0, 0, 1; 1, 4, 4, 7, 1, 2]^n*[0; 2; 4; 12; 40; 128])[1, 1] \\ Charles R Greathouse IV, May 29 2026

Crossrefs

Cf. A126940.

Sequence in context: A170808 A366579 A099214 * A113179 A214761 A391270

Adjacent sequences: A126943 A126944 A126945 * A126947 A126948 A126949

Keyword

nonn,easy

Author

N. J. A. Sloane, Mar 18 2007

Status

approved