

A073409


Largest prime factor of the denominator of the Bernoulli number B(2*n) (A002445).


1



3, 5, 7, 5, 11, 13, 3, 17, 19, 11, 23, 13, 3, 29, 31, 17, 3, 37, 3, 41, 43, 23, 47, 17, 11, 53, 19, 29, 59, 61, 3, 17, 67, 5, 71, 73, 3, 5, 79, 41, 83, 43, 3, 89, 31, 47, 3, 97, 3, 101, 103, 53, 107, 109, 23, 113, 7, 59, 3, 61, 3, 5, 127, 17, 131, 67, 3, 137, 139, 71, 3, 73, 3, 149
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OFFSET

1,1


COMMENTS

Least k such that k!*B(2n) is an integer where B(2n) denotes the 2nth Bernoulli number.
a((p1)/2) = p, where p is odd prime. All odd primes appear in this sequence. The very first appearance of odd prime p is a((p1)/2).  Alexander Adamchuk, Jul 31 2006


LINKS

Table of n, a(n) for n=1..74.


MATHEMATICA

Table[FactorInteger[Denominator[BernoulliB[2n]]][[ 1, 1]], {n, 100}]


PROG

(PARI)
a(n)=
{
my(bd=1);
forprime (p=2, 2*n+1, if( (2*n)%(p1)==0, bd=p ) );
return(bd);
}
/* Joerg Arndt, May 06 2012 */


CROSSREFS

Cf. A005097.
Sequence in context: A141574 A141261 A077129 * A260234 A151548 A256258
Adjacent sequences: A073406 A073407 A073408 * A073410 A073411 A073412


KEYWORD

easy,nonn


AUTHOR

Benoit Cloitre, Aug 23 2002


STATUS

approved



