A022015 a(n)=2a(n-1)+3a(n-2)+2a(n-3)+3a(n-4).

2, 6, 19, 61, 197, 633, 2036, 6548, 21061, 67737, 217861, 700699, 2253638, 7248306, 23312507, 74979305, 241153657, 775615161, 2494587424, 8023265560, 25804984685, 82995786381, 266936820209, 858540765611

Offset

0,1

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,3,2,3).

Formula

G.f.: -(((1+x)*(2+x^2))/(-1+x(2+3*x)*(1+x^2))). - Harvey P. Dale, May 04 2015

Mathematica

LinearRecurrence[{2, 3, 2, 3}, {2, 6, 19, 61}, 30] (* Harvey P. Dale, May 04 2015 *)

Prog

(PARI) a(n)=([0, 1, 0, 0; 0, 0, 1, 0; 0, 0, 0, 1; 3, 2, 3, 2]^n*[2; 6; 19; 61])[1, 1] \\ Charles R Greathouse IV, Jun 01 2026

Crossrefs

Sequence in context: A022041 A018906 A014010 * A138747 A052975 A275943

Adjacent sequences: A022012 A022013 A022014 * A022016 A022017 A022018

Keyword

nonn,easy

Author

R. K. Guy

Status

approved