A105812 Expansion of (1+x-x^2)/(1+x).

1, 0, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1

Offset: 0

Author

Paul Barry, May 04 2005

Keywords

• easy
• sign

Comments

Row sums of number triangle A105810.

Links

• Index entries for linear recurrences with constant coefficients, signature (-1).

Crossrefs

Cf. A033999, A105810.

Programs

Mathematica

LinearRecurrence[{-1}, {1, 0, -1}, 78] (* Ray Chandler, Jul 30 2015 *)

PARI

a(n)=if(n<2,1-n,-(-1)^n) \\ Charles R Greathouse IV, Jun 06 2013

Formula

a(n) = -(-1)^n-binomial(1, n)+3*binomial(0, n).

a(n) = A033999(n-1), n>1. - R. J. Mathar, Aug 28 2008

E.g.f.: 2 - x - exp(-x). - Alejandro J. Becerra Jr., Feb 17 2021