A155181 a(n)=5*a(n-1)+a(n-2), n>2 ; a(0)=1, a(1)=4, a(2)=20 .

1, 4, 20, 104, 540, 2804, 14560, 75604, 392580, 2038504, 10585100, 54964004, 285405120, 1481989604, 7695353140, 39958755304, 207489129660, 1077404403604, 5594511147680, 29049960142004, 150844311857700, 783271519430504

Offset: 0

Author

Philippe Deléham, Jan 21 2009

Keywords

• nonn
• easy

Links

• Paolo Xausa, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (5,1).

Crossrefs

Cf. A155161.

Programs

Mathematica

LinearRecurrence[{5, 1}, {1, 4, 20}, 25] (* Paolo Xausa, Jan 19 2024 *)

Formula

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

a(n) = Sum_{k=0..n} A155161(n,k)*4^k. - Philippe Deléham, Feb 08 2012