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 A043298 Numbers n such that B(6*n) has denominator 42 where B(2k) are the Bernoulli numbers. 1
 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; text; internal format)
 OFFSET 1,2 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, Jul 28 2006 LINKS Enrique PĂ©rez Herrero, Table of n, a(n) for n=1..50000 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, Jul 28 2006 *) CROSSREFS Cf. A051225, A053176. Sequence in context: A120337 A120115 A157995 * A286313 A040068 A096787 Adjacent sequences:  A043295 A043296 A043297 * A043299 A043300 A043301 KEYWORD easy,nonn AUTHOR Benoit Cloitre, Mar 24 2002 EXTENSIONS Corrected and extended by Ralf Stephan, Oct 21 2002 More terms from Alexander Adamchuk, Jul 28 2006 STATUS approved

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Last modified August 13 18:03 EDT 2022. Contains 356107 sequences. (Running on oeis4.)