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 A122270 Numbers m such that the numerator of the Bernoulli number B(m) is divisible by a cube. 5
 250, 686, 750, 1250, 1372, 1750, 2250, 2662, 2744, 2750, 3250, 3430, 3750, 4250, 4394, 4750, 4802, 5250, 5488, 5750, 6250, 6750, 6860, 7250, 7546, 7750, 7986, 8250, 8750, 8788, 8918, 9250, 9604, 9750, 9826 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For each m in the current sequence, the smallest prime whose cube divides the numerator of the Bernoulli number B(m) is listed in A122271. The current sequence is a subset of A090997, which are numbers m such that the numerator of the Bernoulli number B(m) is divisible by a square. A subset of the current sequence is A122272, which are numbers m such that the numerator of the Bernoulli number B(m) is divisible by a fourth power. Conjecture: For all regular primes p > 3 and integers k > 0, the numerator of the Bernoulli number B(2*p^k) is divisible by p^k. Moreover, for all regular primes p > 3 and integers k > 0, m = 2*p^k is the smallest index such that the numerator of the Bernoulli number B(m) is divisible by p^k. Also, for all regular primes p > 3 and integers k > 0, all m such that the numerator of the Bernoulli number B(m) is divisible by p^k are of the form m = 2*s*p^k, where s > 0 is an integer. LINKS The Bernoulli Number Page, Table of factors of the numerators of Bernoulli numbers Bn in the range n = 2..10000, 2018. S. S. Wagstaff, Jr, Prime factors of the absolute values of Bernoulli numerators, 2018. EXAMPLE a(1) = 250 because it is the smallest number m such that numerator(B(m)) == 0 (mod 5^3). Note that 250 = 2*5^3. a(2) = 686 because it is the smallest number m such that numerator(B(m)) == 0 (mod 7^3). Note that 686 = 2*7^3. CROSSREFS Cf. A000367, A090987, A090997, A122271, A122272, A122273. Sequence in context: A267856 A268269 A045185 * A234497 A234491 A249199 Adjacent sequences:  A122267 A122268 A122269 * A122271 A122272 A122273 KEYWORD nonn AUTHOR Alexander Adamchuk, Aug 28 2006 EXTENSIONS Various sections edited by Petros Hadjicostas, May 12 2020 STATUS approved

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Last modified September 29 09:40 EDT 2020. Contains 337428 sequences. (Running on oeis4.)