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.
%I A195732 #35 Aug 26 2024 13:13:16 %S A195732 1,2,3,11,30,62,534,620,803,2436,2669,3975,4530,4827,5294,15987,17589, %T A195732 51960 %N A195732 Numbers k such that 2*(3^k-k)-1 is prime. %C A195732 According to Maple version 14, the next entries are 534, 620 and 803, but these involve primes of 256 and more digits and may not be certified primes. - _R. J. Mathar_, Sep 23 2011 %C A195732 a(19) > 10^5, if it exists. - _Michael S. Branicky_, Aug 26 2024 %e A195732 1 is in the sequence because 2*3^1-2*1-1 = 3 is a prime. %e A195732 2 is in the sequence because 2*3^2-2*2-1 = 13 is a prime. %e A195732 3 is in the sequence because 2*3^3-2*3-1=47 ts a prime. %e A195732 4 is not in the sequence because 2*3^4-2*4-1 = 153 = 3^2*17 is not prime. %o A195732 (PARI) is(n)=ispseudoprime(2*(3^n-n)-1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A195732 Cf. A048473. %K A195732 nonn,more %O A195732 1,2 %A A195732 _Juri-Stepan Gerasimov_, Sep 23 2011 %E A195732 a(10)-a(18) from _Michael S. Branicky_, Jul 14 2023