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A111262 a(n) = (1/n)*Sum_{k=1..n} F(4*k)*B(2*n-2*k)*binomial(2*n,2*k)), where F are Fibonacci numbers and B are Bernoulli numbers. 4
3, 12, 65, 403, 2652, 17889, 121859, 833260, 5706081, 39096531, 267936188, 1836369217, 12586419075, 86267964108, 591287758337, 4052742230419, 27777897084444, 190392509164065, 1304969593244291, 8944394450283436 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Values are always integers.

LINKS

Indranil Ghosh, Table of n, a(n) for n = 1..1194

FORMULA

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

Recurrence: a(n) = 10*a(n-1) - 23*a(n-2) + 10*a(n-3) - a(n-4).

O.g.f.: -x*(-3+18*x-14*x^2+x^3)/((x^2-3*x+1)*(x^2-7*x+1)) = -1+(2-4*x)/(x^2-3*x+1)+(-1+8*x)/(x^2-7*x+1). - R. J. Mathar, Nov 23 2007

a(n) = (Lucas(2*n-1)+2)*Fibonacci(2*n-1) = A162483(n-1)*A001519(n). - Ehren Metcalfe, Jun 04 2019

MATHEMATICA

Table[(1/n)*Sum[Fibonacci[4k]BernoulliB[2n-2k]Binomial[2n, 2k], {k, 1, n}], {n, 1, 20}] (* or *) Table[Fibonacci[4n-2]+2Fibonacci[2n-1], {n, 1, 20}] (* or *) LinearRecurrence[{10, -23, 10, -1}, {3, 12, 65, 403}, 20] (* Indranil Ghosh, Feb 26 2017 *)

PROG

(PARI) a(n)=fibonacci(4*n-2)+2*fibonacci(2*n-1)

CROSSREFS

Cf. A001519.

Sequence in context: A222033 A302195 A196559 * A139134 A216373 A200309

Adjacent sequences:  A111259 A111260 A111261 * A111263 A111264 A111265

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Nov 12 2005, corrected Feb 24 2008

STATUS

approved

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Last modified October 14 18:28 EDT 2019. Contains 328022 sequences. (Running on oeis4.)