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 A119480 Numbers n such that the Bernoulli number B_{4n} has denominator 30. 29
 1, 2, 17, 19, 31, 38, 47, 59, 61, 62, 71, 94, 101, 103, 107, 109, 118, 122, 137, 149, 151, 157, 167, 181, 197, 206, 211, 218, 223, 227, 229, 241, 257, 263, 269, 271, 283, 289, 302, 311, 313, 314, 317, 331, 334, 337, 347, 349, 353, 361, 362, 367, 379 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Most a(n) are primes from A043297(n) except for a(1) = 1 and composite a(n) for n=6,10,12,17,18,26,28,38,39,42,45,50,51, ... a(6) = 38 = 2*19, a(10) = 62 = 2*31, a(12) = 94 = 2*47, a(17) = 118 = 2*59, a(18) = 122 = 2*61, a(26) = 206 = 2*103, a(28) = 218 = 2*109, a(38) = 289 = 17*17, a(39) = 302 = 2*151, a(42) = 314 = 2*157, a(45) = 334 = 2*167, a(50) = 361 = 19*19, a(51) = 362 = 2*181, ... It appears that most composite a(n) are the doubles of some primes from A043297(n) belonging to A081092[n] and A045404[n] - Primes congruent to {3, 4, 5, 6} mod 7. The rest of composite a(n) are the squares of the primes from A043297(n). Some a(n) are the products of different primes from A043297(n), for example a(77) = 527 = 17*31. a(n) belong to A045402 Primes congruent to {1, 3, 4, 5, 6} mod 7. a(n) is a subset of A053176 Primes p such that 2p+1 is composite, A045979 Bernoulli number B_{2n} has denominator 6, A090863 Numbers n such that F(n+1)*F(n-1)*B(2n) is an integer, where F(k)=k-th Fibonacci number and B(2k)=2k-th Bernoulli number. - Alexander Adamchuk, Jul 27 2006 LINKS E. Pérez Herrero, Table of n, a(n) for n=1..50000 FORMULA a(n) = A051225[n]/2. MATHEMATICA Select[Range@ 400, Denominator@ BernoulliB[4 #] == 30 &] (* Michael De Vlieger, Aug 09 2017 *) CROSSREFS Cf. A043297, A051225, A051222, A051230, A045404. Cf. A045402, A053176, A045979, A090863. Sequence in context: A176902 A153261 A080115 * A043297 A018569 A022118 Adjacent sequences:  A119477 A119478 A119479 * A119481 A119482 A119483 KEYWORD nonn AUTHOR Alexander Adamchuk, Jul 26 2006 STATUS approved

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Last modified May 26 17:40 EDT 2020. Contains 334630 sequences. (Running on oeis4.)