A060976 Odd nonprimes c which divide Bernoulli(2*c).

1, 25, 35, 49, 65, 77, 85, 91, 95, 115, 119, 121, 125, 133, 143, 145, 155, 161, 169, 175, 185, 187, 203, 205, 209, 215, 217, 221, 235, 245, 247, 259, 265, 287, 289, 295, 299, 301, 305, 319, 323, 325, 329, 335, 341, 343, 355, 361, 365, 371, 377, 391, 395, 403

Offset: 1

Author

Robert G. Wilson v, May 09 2001

Keywords

• nonn

Comments

a(n) == +- 1 (mod 6).

First differences: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24. - Robert G. Wilson v, Jan 26 2017

Links

• Robert G. Wilson v, Table of n, a(n) for n = 1..5373

Programs

Mathematica

Do[ If[ Mod[ Numerator[ BernoulliB[ 2*n ] ], 2n ] == 0 && ! PrimeQ[ n ], Print[ n ] ], {n, 1, 250, 2} ]

PARI

select(n->n%2&!isprime(n)&numerator(bernfrac(2*n))%n==0,vector(1000,i,i)) \\ Charles R Greathouse IV, May 26 2011