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 A089623 #14 Sep 08 2022 08:45:12 %S A089623 1,2,4,6,8,12,14,18,20,26,28,32,34,36,42,46,48,54,60,62,68,70,74,76, %T A089623 88,92,102,106,116,118,120,126,130,134,138,144,154,160,168,172,176, %U A089623 182,190,204,210,216,222,230,232,236,238,246,252,256,258,264,266,272 %N A089623 Numbers n such that n^2 + 2n - 1 is prime. %C A089623 Equivalently, numbers n such that (n+1)^2 - 2 is prime. %D A089623 M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988. %D A089623 Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997. %H A089623 Vincenzo Librandi, <a href="/A089623/b089623.txt">Table of n, a(n) for n = 1..1000</a> %F A089623 a(n) = 2*A088572(n). %t A089623 Select[Range[1000], PrimeQ[#^2 + 2 # - 1] &] (* _Vincenzo Librandi_, May 24 2014 *) %o A089623 (Magma) [n: n in [0..400] | IsPrime(n^2+2*n-1)]; // _Vincenzo Librandi_, Dec 17 2010 %o A089623 (PARI) is(n)=isprime(n^2+2*n-1) \\ _Charles R Greathouse IV_, Jun 05 2017 %Y A089623 Cf. A088572. See A028871 for the actual primes. %K A089623 nonn,easy %O A089623 1,2 %A A089623 _Giovanni Teofilatto_, Dec 31 2003 %E A089623 Corrected (1 prepended and 96 replaced with 92) by _Vincenzo Librandi_, Dec 17 2010