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A289719 a(n) = (n/2)*binomial(2*n, n) + 1. 2
1, 2, 7, 31, 141, 631, 2773, 12013, 51481, 218791, 923781, 3879877, 16224937, 67603901, 280816201, 1163381401, 4808643121, 19835652871, 81676217701, 335780006101, 1378465288201, 5651707681621, 23145088600921, 94684453367401, 386971244197201, 1580132580471901 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..500

A. Umar, Combinatorial Results for Semigroups of Orientation-Preserving Partial Transformations, J. Int. Seq. 14 (2011) # 11.7.5, corollary 37, tables 4.1 and 4.2

FORMULA

a(n) = 1 + A002457(n-1).

MAPLE

seq(1+n/2*binomial(2*n, n), n=0..20) ;

MATHEMATICA

Table[(n/2) Binomial[2 n, n] + 1, {n, 0, 20}] (* Michael De Vlieger, Sep 05 2017 *)

PROG

(GAP)

A289719:=List([0..10^2], n->(n/2)*Binomial(2*n, n)+1); # Muniru A Asiru, Sep 03 2017

(PARI) a(n) = {n*binomial(2*n, n)/2 + 1} \\ Andrew Howroyd, Apr 26 2020

CROSSREFS

Cf. A002457, A289720.

Sequence in context: A343532 A034698 A115605 * A114198 A055836 A076177

Adjacent sequences:  A289716 A289717 A289718 * A289720 A289721 A289722

KEYWORD

nonn,easy

AUTHOR

R. J. Mathar, Sep 02 2017

EXTENSIONS

Terms a(21) and beyond from Andrew Howroyd, Apr 26 2020

STATUS

approved

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Last modified October 16 05:41 EDT 2021. Contains 348035 sequences. (Running on oeis4.)