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A043298
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Numbers n such that B(6*n) has denominator 42 where B(2k) are the Bernoulli numbers.
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1
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1, 19, 31, 43, 59, 67, 71, 79, 97, 109, 127, 139, 149, 157, 163, 167, 193, 197, 199, 211, 223, 227, 229, 269, 307, 317, 337, 349, 353, 361, 379, 383, 389, 401, 409, 421, 433, 439, 449, 457, 463, 479, 487, 499, 521, 523, 541, 547, 563, 569, 571, 587, 589, 599
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Except for 1 and 361=19^2 terms listed are primes.
Most a(n) are primes p such that 2p+1 is composite A053176. Nonprime a(n) (except a(1) = 1) are the powers or the products of primes from a(n). For example, 361 = 19^2, 589 = 19*31, 961 = 31^2, 1333 = 31*43, 1849 = 43^2, 2071 = 19*109, 2077 = 31*67, 2201 = 31*71, 2449 = 31*79, 2537 = 43*59, 2641 = 19*139, 2881 = 43*67, 2983 = 19*157, 3053 = 43*71, 3173 = 19*167, ..., 6859 = 19^3. - Alexander Adamchuk (alex(AT)kolmogorov.com), Jul 28 2006
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LINKS
| E. Perez Herrero, Table of n, a(n) for n=1..50000
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MATHEMATICA
| Do[s=1+Divisors[n]; s1=Flatten[Position[PrimeQ[s], True]]; s2=Part[s, s1]; If[Equal[s2, {2, 3, 7}], Print[n/6]], {n, 1, 10000}] - Alexander Adamchuk (alex(AT)kolmogorov.com), Jul 28 2006
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CROSSREFS
| Cf. A051225, A053176.
Sequence in context: A120337 A120115 A157995 * A040068 A096787 A104006
Adjacent sequences: A043295 A043296 A043297 * A043299 A043300 A043301
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 24 2002
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EXTENSIONS
| Corrected and extended by Ralf Stephan (ralf(AT)ark.in-berlin.de), Oct 21 2002
More terms from Alexander Adamchuk (alex(AT)kolmogorov.com), Jul 28 2006
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