A026955 a(n) = Sum_{k=0..n} (k+1) * T(n,k), with T given by A026386.

1, 3, 8, 25, 60, 175, 400, 1125, 2500, 6875, 15000, 40625, 87500, 234375, 500000, 1328125, 2812500, 7421875, 15625000, 41015625, 85937500, 224609375, 468750000, 1220703125, 2539062500, 6591796875, 13671875000, 35400390625

Offset

0,2

Links

Table of n, a(n) for n=0..27.

Formula

For n>0, a(n) = (n+2)[7-3(-1)^n]/10 * 5^[n/2].

Conjecture: a(n) = 10*a(n-2)-25*a(n-4) for n>4. G.f.: (5*x^4-5*x^3-2*x^2+3*x+1)/(5*x^2-1)^2. [Colin Barker, Oct 13 2012]

Crossrefs

Sequence in context: A076049 A026970 A026980 * A093900 A018789 A203413

Adjacent sequences: A026952 A026953 A026954 * A026956 A026957 A026958

Keyword

nonn

Author

Clark Kimberling

Status

approved