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.

A110931 Numbers k such that 2*k^k - 1 is prime.

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%I A110931 #41 Jul 28 2022 20:57:02
%S A110931 2,3,357,1400,205731,296598
%N A110931 Numbers k such that 2*k^k - 1 is prime.
%C A110931 a(5) > 4000. - _Ray G. Opao_, Oct 23 2014
%C A110931 a(5) > 101000. - _Serge Batalov_, Apr 13 2018
%e A110931 3 is in the sequence since 2*3^3 - 1 = 53 is prime.
%t A110931 Select[Range[1000], PrimeQ[2*#^# - 1] &] (* _Vaclav Kotesovec_, Oct 31 2014 *)
%o A110931 (PARI) for(n=1,2000,1;if(isprime(2*n^n-1),print(n))) \\ _Ray G. Opao_, Oct 23 2014
%o A110931 (Magma) [n: n in [0..500] | IsPrime(2*n^n-1)]; // _Vincenzo Librandi_, Nov 01 2014
%Y A110931 Numbers k such that b*k^k - b + 1 is prime: this sequence (b=2), A301521 (b=4), A302123 (b=6).
%Y A110931 Cf. A110932, A062207, A108318.
%K A110931 more,nonn,hard
%O A110931 1,1
%A A110931 _Ray G. Opao_, Sep 25 2005
%E A110931 a(5-6) from _Ryan Propper_, Jul 24-28 2022