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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
OFFSET
0,2
LINKS
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
Sequence in context: A343532 A034698 A115605 * A114198 A349769 A358963
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Sep 02 2017
EXTENSIONS
Terms a(21) and beyond from Andrew Howroyd, Apr 26 2020
STATUS
approved