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

1,1

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.

Links

Table of n, a(n) for n=1..61.

Formula

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

Mathematica

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

Prog

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

Crossrefs

Cf. A060308, A151799.

Sequence in context: A229470 A157829 A020581 * A177512 A118751 A173494

Adjacent sequences: A081256 A081257 A081258 * A081260 A081261 A081262

Keyword

nonn

Author

Benoit Cloitre, Apr 20 2003

Status

approved