A110315 Diagonal sums of the Fibonacci related number triangle A110314.

1, -1, -1, -2, -5, -3, -11, -4, -19, -5, -29, -6, -41, -7, -55, -8, -71, -9, -89, -10, -109, -11, -131, -12, -155, -13, -181, -14, -209, -15, -239, -16, -271, -17, -305, -18, -341, -19, -379, -20, -419, -21, -461, -22, -505, -23, -551, -24, -599, -25, -649

Offset: 0

Author

Paul Barry, Jul 19 2005

Keywords

• easy
• sign

Links

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

Formula

G.f.: (1-x-4x^2+x^3+x^4)/((1-x)^3*(1+x)^3).

a(n) = 3a(n-2)-3a(n-4)+a(n-6).

a(n) = (6-n^2)(-1)^n/8-(n^2+4n-2)/8.

a(2n) = A110331(n). - R. J. Mathar, Aug 22 2012