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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.)