A081259 a(n) is the smallest k such that C(3n,n) divides k!.

2, 5, 7, 11, 13, 17, 19, 23, 23, 29, 31, 31, 37, 41, 43, 47, 47, 53, 53, 59, 61, 61, 67, 71, 73, 73, 79, 83, 83, 89, 89, 89, 97, 101, 103, 107, 109, 113, 113, 113, 113, 113, 127, 131, 131, 137, 139, 139, 139, 149, 151, 151, 157, 157, 163, 167, 167, 173, 173, 179, 181

Offset: 1

Author

Benoit Cloitre, Apr 20 2003

Keywords

• nonn

Comments

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

Crossrefs

Cf. A060308, A151799.

Programs

Mathematica

NextPrime[3Range[70],-1] (* Harvey P. Dale, Oct 20 2011 *)

PARI

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

Formula

a(n) = A151799(3n). - R. J. Mathar, Jul 18 2015