A104581 - OEIS

A104581

Expansion of g.f. 1/(1 + x + x^3 + x^4).

1, -1, 1, -2, 2, -2, 3, -3, 3, -4, 4, -4, 5, -5, 5, -6, 6, -6, 7, -7, 7, -8, 8, -8, 9, -9, 9, -10, 10, -10, 11, -11, 11, -12, 12, -12, 13, -13, 13, -14, 14, -14, 15, -15, 15, -16, 16, -16, 17, -17, 17, -18, 18, -18, 19, -19, 19, -20, 20, -20, 21, -21, 21, -22, 22, -22, 23, -23, 23, -24, 24, -24, 25, -25, 25, -26, 26, -26

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OFFSET

0,4

COMMENTS

Diagonal sums of Riordan array (1/(1+x+x^2+x^3+x^4),x/(1+x+x^2+x^3+x^4)).

Convolution of (n+1)(-1)^n and A010892.

LINKS

Table of n, a(n) for n=0..77.

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

FORMULA

a(n) = floor((n + 3)/3)*(-1)^n.

a(n) = Sum_{k=0..n} ((n - k + 1)(-1)^(n-k)*2sin(Pi*k/3 + Pi/3)/sqrt(3)).