A081259 - OEIS

%I #11 Jul 18 2015 08:40:27

%S 2,5,7,11,13,17,19,23,23,29,31,31,37,41,43,47,47,53,53,59,61,61,67,71,

%T 73,73,79,83,83,89,89,89,97,101,103,107,109,113,113,113,113,113,127,

%U 131,131,137,139,139,139,149,151,151,157,157,163,167,167,173,173,179,181

%N a(n) is the smallest k such that C(3n,n) divides k!.

%C a(n) is the largest prime < 3n. More generally the smallest k such that C(mn,n) divides k! is the largest prime < mn.

%F a(n) = A151799(3n). - _R. J. Mathar_, Jul 18 2015

%t NextPrime[3Range[70],-1] (* _Harvey P. Dale_, Oct 20 2011 *)

%o (PARI) a(n)=if(n<0,0,s=1; while(k!%binomial(3*n,n)>0,k++); k)

%Y Cf. A060308, A151799.

%K nonn

%O 1,1

%A _Benoit Cloitre_, Apr 20 2003