A026950 a(n) = Sum_{k=0..n} (k+1) * T(n,k), with T given by A026374.

1, 3, 10, 25, 75, 175, 500, 1125, 3125, 6875, 18750, 40625, 109375, 234375, 625000, 1328125, 3515625, 7421875, 19531250, 41015625, 107421875, 224609375, 585937500, 1220703125, 3173828125, 6591796875, 17089843750, 35400390625, 91552734375, 189208984375, 488281250000

Offset

0,2

Links

Andrew Howroyd, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,10,0,-25).

Formula

a(n) = (n + 2) * (7 + 3*(-1)^n) * 5^floor((n-1)/2) / 4.

From Colin Barker, Oct 13 2012: (Start)

a(n) = 10*a(n-2) - 25*a(n-4).

G.f.: -(5*x^3-3*x-1)/(5*x^2-1)^2. (End)

Prog

(PARI) a(n) = (n + 2) * (7 + 3*(-1)^n) * 5^((n-1)\2) / 4 \\ Andrew Howroyd, Dec 27 2024

Crossrefs

Cf. A026374.

Sequence in context: A027227 A319748 A027228 * A095052 A196984 A131433

Adjacent sequences: A026947 A026948 A026949 * A026951 A026952 A026953

Keyword

nonn,easy

Author

Clark Kimberling

Extensions

a(28) onwards from Andrew Howroyd, Dec 27 2024

Status

approved