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 A233578 n >= 2 such that the denominator/6 of Bernoulli(n) is congruent to {1, 5, 7, 13 or 19} modulo 30. 3
 2, 4, 6, 8, 12, 14, 18, 24, 26, 34, 36, 38, 40, 42, 54, 62, 68, 70, 72, 74, 76, 78, 86, 88, 94, 98, 100, 102, 108, 110, 114, 118, 120, 122, 124, 126, 130, 134, 142, 146, 152, 158, 162, 182, 186, 188, 190, 194, 196, 202, 204, 206, 208, 210, 214, 216, 218, 220, 222, 228, 230, 232, 234 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Conjecture: for these and only these n, the absolute value of the numerator of Bernoulli(n) is congruent 1 modulo 6.  If my conjecture is true, then you can obtain the residue modulo 6 of the abs. value of Bernoulli numerators by calculating their denominators/6 modulo 30.  Program uses the von Staudt-Clausen Theorem.  None of these n are in the complementary sequence, A233579 (n such that the denominator/6 of Bernoulli(n) is congruent to {11, 17, 23, 25 or 29} modulo 30.  I have checked and verified that, up to n = 50446, the union of A233578 and A233579 is all even numbers >= 2. LINKS Michael G. Kaarhus, Table of n, a(n) for n = 1..10000 M. G. Kaarhus, Splitting the Bernoulli Numbers EXAMPLE 100 is in this sequence, because the denominator of Bernoulli(100) = 33330, and 33330/6 = 5555, and 5555 is congruent to 5 modulo 30.  As for the conjecture, the abs. val. of the numerator of Bernoulli(100) is congruent to 1 modulo 6. PROG (Maxima) float(true)\$ load(basic)\$ i:[1]\$ n:2\$ for r:1 thru 10000 step 0 do (for p:3 while p-1<=n step 0 do (p:next_prime(p), if mod(n, p-1)=0 then push(p, i)), d:(product(i[k], k, 1, length(i))), x:mod(d, 30), if (x=1 or x=5 or x=7 or x=13 or x=19) then (print(r, ", ", n), r:r+1), i:[1], n:n+2)\$ CROSSREFS Cf. A233579, subsequence of A005843. Sequence in context: A089681 A227308 A214294 * A057220 A294847 A082742 Adjacent sequences:  A233575 A233576 A233577 * A233579 A233580 A233581 KEYWORD nonn AUTHOR Michael G. Kaarhus, Dec 13 2013 STATUS approved

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Last modified February 23 21:20 EST 2020. Contains 332195 sequences. (Running on oeis4.)