OFFSET
1,2
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
Vaclav Kotesovec, Plot of a(n)/n for n = 1..60000
FORMULA
It seems that a(n) is asymptotic to C*n with C=2.3...
MATHEMATICA
Select[Range[200], Divisible[Binomial[2*#, #], EulerPhi[#]] &] (* Vaclav Kotesovec, Feb 15 2019 *)
PROG
(PARI) isok(n) = ! (binomial(2*n, n) % eulerphi(n)); \\ Michel Marcus, Nov 28 2013
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 21 2002
STATUS
approved