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 A195815 #22 Aug 25 2024 21:07:42 %S A195815 1,2,3,5,11,188,509,1730,2571,3402,4407,9890,18609,20456,32529,38124, %T A195815 95087 %N A195815 Numbers k such that 2*(3^k-2*k)+1 is prime. %C A195815 The associated primes are 3, 11, 43, 467, 354251,.... %e A195815 a(1)=1 because 2*(3^1-2*1)+1=3 is a prime, a(2)=2 because 2*(3^2-2*2)+1=11 is a prime, a(3)=3 because 2*(3^3-2*3)+1=43 is a prime, a(4)=5 because 2*(3^5-2*5)+1=467 is a prime, a(5)=11 because 2*(3^11-2*11)+1=354251 is a prime. %o A195815 (PARI) is(n)=ispseudoprime(2*(3^n-2*n)+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A195815 Cf. A195732. %K A195815 nonn,more %O A195815 1,2 %A A195815 _Juri-Stepan Gerasimov_, Sep 24 2011 %E A195815 a(9)-a(16) from _Michael S. Branicky_, Jul 15 2023 %E A195815 a(17) from _Michael S. Branicky_, Aug 25 2024