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 A244453 Prime factors of 2^A054723(n)-1, ordered by increasing n, then by increasing size of the factors. 1
 23, 89, 47, 178481, 233, 1103, 2089, 223, 616318177, 13367, 164511353, 431, 9719, 2099863, 2351, 4513, 13264529, 6361, 69431, 20394401, 179951, 3203431780337, 193707721, 761838257287, 228479, 48544121, 212885833 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Subsequence of A060443. Prime factors of composite Mersenne numbers; A089162 with the Mersenne primes A000668 removed. - Jens Kruse Andersen, Jul 11 2014 LINKS Jens Kruse Andersen, Table of n, a(n) for n = 1..577 Sergey Nikitin, Euler-Fermat algorithm and some of its applications, 2018. Sam Wagstaff, The Cunningham Project EXAMPLE A054723(1) = 11. 2^11-1 = 2047 = 23*89. - Jens Kruse Andersen, Jul 11 2014 Triangle begins: 23, 89; 47, 178481; 233, 1103, 2089; 223, 616318177; 13367, 164511353; 431, 9719, 2099863; 2351, 4513, 13264529; 6361, 69431, 20394401; MATHEMATICA Map[FactorInteger, Select[2^Prime@Range@20 - 1, CompositeQ]][[All, All, 1]] // Flatten (* Michael De Vlieger, Nov 20 2018 *) PROG (PARI) forprime(n=1, 100, m=2^n-1; if(!isprime(m), f=factor(m); for(i=1, #f~, print1(f[i, 1]", ")))) \\ Jens Kruse Andersen, Jul 11 2014 CROSSREFS Cf. A003260, A016047, A046800, A089162. Sequence in context: A044591 A050255 A014088 * A158537 A117049 A142062 Adjacent sequences:  A244450 A244451 A244452 * A244454 A244455 A244456 KEYWORD nonn,tabf AUTHOR Felix FrÃ¶hlich, Jun 28 2014 STATUS approved

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Last modified August 3 02:48 EDT 2021. Contains 346435 sequences. (Running on oeis4.)