A155041 Diagonal sums of symmetric (1,-1)-triangle A155040.

1, 1, 2, 0, 1, -1, 2, 0, 3, -1, 2, -2, 3, -1, 4, -2, 3, -3, 4, -2, 5, -3, 4, -4, 5, -3, 6, -4, 5, -5, 6, -4, 7, -5, 6, -6, 7, -5, 8, -6, 7, -7, 8, -6, 9, -7, 8, -8, 9, -7, 10, -8, 9, -9, 10, -8, 11, -9, 10, -10, 11, -9, 12, -10, 11, -11, 12, -10, 13, -11, 12, -12, 13, -11, 14, -12, 13

Offset: 0

Author

Paul Barry, Jan 19 2009

Keywords

• easy
• sign

Comments

First differences of A155041 are (-1)^n*A008611.

Links

• Index entries for linear recurrences with constant coefficients, signature (0,1,-1,0,1).

Formula

G.f.: (1+x+x^2)/(1-x^2+x^3-x^5);

a(2n)=A008611(n+2)=[x^n](1+x-x^2)/(1-x-x^3+x^4); a(2n+1)=[x^n](1-x-x^2)/(1-x-x^3+x^4).