A110326 Diagonal sums of triangle A110324.

1, -1, -3, -2, -11, -3, -23, -4, -39, -5, -59, -6, -83, -7, -111, -8, -143, -9, -179, -10, -219, -11, -263, -12, -311, -13, -363, -14, -419, -15, -479, -16, -543, -17, -611, -18, -683, -19, -759, -20, -839, -21, -923, -22, -1011, -23, -1103, -24, -1199, -25, -1299, -26, -1403, -27, -1511, -28, -1623, -29, -1739

Offset: 0

Author

Paul Barry, Jul 20 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-6x^2+x^3+x^4)/((1+x)^3(1-x)^3); a(n)=3a(n-2)-3a(n-4)+a(n-6); a(n)=-(n^2+3n-1)/4-(n^2+n-3)(-1)^n/4.