A110332 Diagonal sums of number a triangle related to the Pell numbers.

1, -2, -1, -4, -5, -6, -11, -8, -19, -10, -29, -12, -41, -14, -55, -16, -71, -18, -89, -20, -109, -22, -131, -24, -155, -26, -181, -28, -209, -30, -239, -32, -271, -34, -305, -36, -341, -38, -379, -40, -419, -42, -461, -44, -505, -46, -551, -48, -599, -50, -649, -52, -701, -54, -755, -56, -811, -58, -869, -60, -929

Offset: 0

Author

Paul Barry, Jul 20 2005

Keywords

• easy
• sign

Comments

Diagonal sums of number triangle A110330.

Links

• Index entries for linear recurrences with constant coefficients, signature (0,3,0,-3,0,1)

Crossrefs

Cf. A028387 (bisection), A005843 (bisection).

Formula

G.f.: (1-2x-4x^2+2x^3+x^4)/((1+x)^3(1-x)^3); a(n)=3a(n-2)-3a(n-4)+a(n-6); a(n)=-n(n+6)/8-(n^2-2n-8)(-1)^n/8.