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A236407 a(n) = 2*Sum_{k=0..n-1} C(n-1,k)*C(n+k,k) + n. 1
0, 3, 10, 41, 196, 1007, 5342, 28821, 157192, 864155, 4780018, 26572097, 148321356, 830764807, 4666890950, 26283115053, 148348809232, 838944980531, 4752575891162, 26964373486425, 153196621856212, 871460014012703, 4962895187697070, 28292329581548741 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

J. Brzozowski, M. Szykula, Large Aperiodic Semigroups, arXiv:1401.0157 [cs.FL], 2013 (Tables 1, 2).

FORMULA

a(n) = A002003(n) + n.

Conjecture: n*(n-3)*a(n) -4*(2*n-1)*(n-3)*a(n-1) +2*(7*n^2-28*n+20)*a(n-2) -4*(n-1)*(2*n-7)*a(n-3) +(n-1)*(n-4)*a(n-4)=0. - R. J. Mathar, Feb 01 2014

Recurrence: (n-2)*n*(2*n^2 - 8*n + 7)*a(n) = (14*n^4 - 88*n^3 + 189*n^2 - 158*n + 39)*a(n-1) - (14*n^4 - 80*n^3 + 153*n^2 - 112*n + 24)*a(n-2) + (n-3)*(n-1)*(2*n^2 - 4*n + 1)*a(n-3). - Vaclav Kotesovec, Feb 14 2014

a(n) ~ 2^(-3/4) * (3+2*sqrt(2))^n / sqrt(Pi*n). - Vaclav Kotesovec, Feb 14 2014

MATHEMATICA

Table[2*Sum[Binomial[n-1, k]*Binomial[n+k, k], {k, 0, n-1}]+n, {n, 0, 20}] (* Vaclav Kotesovec, Feb 14 2014 *)

Flatten[{0, Table[n+2*Hypergeometric2F1[1-n, 1+n, 1, -1], {n, 1, 20}]}] (* Vaclav Kotesovec, Feb 14 2014 *)

PROG

(PARI) for(n=0, 25, print1(n + 2*sum(k=0, n-1, binomial(n-1, k) * binomial(n+k, k)), ", ")) \\ G. C. Greubel, Jun 01 2017

CROSSREFS

Cf. A002003.

Sequence in context: A140046 A260772 A116540 * A000248 A245504 A305405

Adjacent sequences:  A236404 A236405 A236406 * A236408 A236409 A236410

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jan 31 2014

STATUS

approved

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Last modified June 18 11:24 EDT 2018. Contains 305554 sequences. (Running on oeis4.)