A027984 a(n) = Sum{T(n,k)*T(n,n+k)}, 0<=k<=n, T given by A027960.

1, 6, 20, 58, 161, 436, 1165, 3088, 8146, 21426, 56255, 147538, 386681, 1013026, 2653240, 6948058, 18193141, 47634936, 124717445, 326526748, 854877926, 2238131506, 5859556195, 15340601158, 40162350961, 105146619486, 275277778940

Offset

0,2

Links

Table of n, a(n) for n=0..26.

Formula

Conjectures from Colin Barker, Feb 25 2015: (Start)

a(n) = 4*a(n-1)-3*a(n-2)-2*a(n-3)+a(n-4).

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

(End)

Prog

(PARI) T027960(r, n) = if(r<0||n>2*r, return(0)); if(n==0||n==2*r, return(1)); if(n==1, 3, T027960(r-1, n-1)+T027960(r-1, n-2));
a(n) = sum(k=0, n, T027960(n, k)*T027960(n, n+k)); \\ Michel Marcus, Feb 25 2015

Crossrefs

Sequence in context: A127982 A109164 A212689 * A342313 A309294 A018808

Adjacent sequences: A027981 A027982 A027983 * A027985 A027986 A027987

Keyword

nonn

Author

Clark Kimberling

Status

approved