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%I #31 Apr 18 2024 09:33:48
%S 0,1,3,7,3,5,31,3,7,127,3,5,17,7,73,3,11,31,23,89,3,5,7,13,8191,3,43,
%T 127,7,31,151,3,5,17,257,131071,3,7,19,73,524287,3,5,11,31,41,7,127,
%U 337,3,23,89,683,47,178481,3,5,7,13,17,241
%N Table T(n,k) in which n-th row lists prime factors of 2^n - 1 (n >= 2), without repetition.
%C For n > 1, the length of row n is A046800(n). - _T. D. Noe_, Aug 06 2007
%D J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.
%H T. D. Noe, <a href="/A060443/b060443.txt">Rows n=0..500 of triangle, flattened</a> (derived from Brillhart et al.)
%H Joerg Arndt, <a href="/A001265/a001265.txt">Rows n=1..1200 of triangle when repetitions are included</a> (derived from Brillhart et al.)
%H J. Brillhart et al., <a href="http://dx.doi.org/10.1090/conm/022">Factorizations of b^n +- 1</a>, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
%H Jeroen Demeyer, <a href="http://cage.ugent.be/~jdemeyer/cunningham/">Machine-readable Cunningham Tables</a> [Broken link]
%H S. S. Wagstaff, Jr., <a href="http://www.cerias.purdue.edu/homes/ssw/cun/index.html">The Cunningham Project</a>
%H Chai Wah Wu, <a href="https://github.com/postvakje/Reformatted-Cunningham-Project-tables">Tables from the Cunningham Project in machine-readable JSON format.</a>
%e From _Wolfdieter Lang_, Sep 23 2017: (Start)
%e The irregular triangle T(n,k) begins for n >= 2:
%e n\k 1 2 3 4 5
%e 2: 3
%e 3: 7
%e 4: 3 5
%e 5: 31
%e 6: 3 7
%e 7: 127
%e 8: 3 5 17
%e 9: 7 73
%e 10: 3 11 31
%e 11: 23 89
%e 12: 3 5 7 13
%e 13: 8191
%e 14: 3 43 127
%e 15: 7 31 151
%e 16: 3 5 17 257
%e 17: 131071
%e 18: 3 7 19 73
%e 19: 524287
%e 20: 3 5 11 31 41
%e ... (End)
%t Array[FactorInteger[2^# - 1][[All, 1]] &, 25, 0] (* _Paolo Xausa_, Apr 18 2024 *)
%Y Cf. A001265, A064078.
%K nonn,tabf,changed
%O 0,3
%A _N. J. A. Sloane_
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