OFFSET
1,2
COMMENTS
Original name was: Numbers n such that gcd(2*n,C(2*n,n))=2*n.
For n a prime power (see A000961) we have gcd(2*n,C(2*n,n))=2. - Arkadiusz Wesolowski, Jul 01 2012
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
FORMULA
Appears to be A067348(n)/2. - Benoit Cloitre, Mar 21 2003
Terms >1 are given by A002503+1. - Benoit Cloitre, Dec 09 2017
MATHEMATICA
Select[Range[500], IntegerQ[(2 # - 1)!/#!^2] &] (* Arkadiusz Wesolowski, Jul 01 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 13 2000
EXTENSIONS
Name changed by Arkadiusz Wesolowski, Jul 01 2012
STATUS
approved