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
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Sep 02 2017
EXTENSIONS
Terms a(21) and beyond from Andrew Howroyd, Apr 26 2020
STATUS
approved