cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A316908 a(n) is the smallest k with n prime factors such that 2^(k-1) == 1 (mod k) and p-1 does not divide k-1 for every prime p dividing k.

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%I A316908 #21 Jun 09 2020 03:36:56
%S A316908 7957,617093,134564501,384266404601,8748670222601,6105991025919737,
%T A316908 901196605940857381
%N A316908 a(n) is the smallest k with n prime factors such that 2^(k-1) == 1 (mod k) and p-1 does not divide k-1 for every prime p dividing k.
%C A316908 Conjecture: a(n) > A006931(n) for every n > 2.
%C A316908 a(6)-a(8) derived from Feitsma's tables of pseudoprimes. a(9) > 2^64. - _Giovanni Resta_, Jul 19 2018
%C A316908 From _Daniel Suteu_, Jun 08 2020: (Start)
%C A316908 a(9)  <= 521957994426556057126261,
%C A316908 a(10) <= 1315856103949347820015303981,
%C A316908 a(11) <= 6357507186189933506573017225316941,
%C A316908 a(12) <= 77822245466150976053960303855104674781. (End)
%H A316908 Jan Feitsma and William Galway, <a href="http://www.cecm.sfu.ca/Pseudoprimes/index-2-to-64.html">Tables of pseudoprimes and related data</a>
%Y A316908 Cf. A001567, A121707, A316907.
%K A316908 nonn,more
%O A316908 2,1
%A A316908 _Thomas Ordowski_, Jul 16 2018
%E A316908 More terms from _Michel Marcus_, Jul 16 2018
%E A316908 a(6)-a(8) from _Giovanni Resta_, Jul 19 2018