A165625 a(n)=(5/3)*(1+2*(-5)^(n-1)).

1, 5, -15, 85, -415, 2085, -10415, 52085, -260415, 1302085, -6510415, 32552085, -162760415, 813802085, -4069010415, 20345052085, -101725260415, 508626302085, -2543131510415, 12715657552085, -63578287760415

Offset: 0

Author

Philippe Deléham, Sep 22 2009

Keywords

• easy
• sign

Links

• Index entries for linear recurrences with constant coefficients, signature (-4,5).

Crossrefs

Cf. A083217, A084247, A165553, A165622

Programs

Mathematica

LinearRecurrence[{-4,5},{1,5},30] (* Harvey P. Dale, Nov 28 2015 *)

Formula

a(n)=(-5)*a(n-1)+10 with a(0)=1. a(0)=1, a(1)=5, a(n)=5*a(n-2)-4*a(n-1). G.f.: (1+9x)/(1+4x-5x^2). a(n)= Sum_{k, 0<=k<=n} A112555(n,k)*4^(n-k).