OFFSET
4,2
PROG
(PARI) \\ here cat(n) is A000108(n).
cat(n)={binomial(2*n, n)/(n+1)}
a(n)={if(n%2==0, cat(n/2) + 2*cat(n/2-1) - 3, 2*cat(n\2) - 2)} \\ Andrew Howroyd, Mar 13 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 07 2021
EXTENSIONS
Terms a(11) and beyond from Andrew Howroyd, Mar 13 2021
STATUS
approved