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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Least k such that k!*B(2n) is an integer where B(2n) denotes the 2n-th Bernoulli number.

a((p-1)/2) = p, where p is odd prime. All odd primes appear in this sequence. The very first appearance of odd prime p is a((p-1)/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)%(p-1)==0, bd=p ) );

    return(bd);

}

/* Joerg Arndt, May 06 2012 */

CROSSREFS

Cf. A005097.

Sequence in context: A141574 A141261 A077129 * A151548 A177433 A214091

Adjacent sequences:  A073406 A073407 A073408 * A073410 A073411 A073412

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Aug 23 2002

STATUS

approved

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Last modified April 25 00:50 EDT 2014. Contains 240991 sequences.