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 A138220 #21 Sep 08 2022 08:45:33 %S A138220 3,4,5,6,7,8,9,10,14,19,23,25,26,31,32,36,38,43,44,45,47,48,62,64,66, %T A138220 77,81,82,85,90,91,92,95,108,112,113,116,122,129,130,136,138,139,142, %U A138220 147,151,153,155,164,178,179,181,183,185,190,192,195,196,199,201,202,204 %N A138220 Numbers k such that 900*k^2 + 1 is prime. %C A138220 Includes all terms from A125251. %C A138220 Conjecture: (30*k)^(2^m)+1 is prime for some numbers k at all values of m >= 0. - _Richard R. Forberg_, Feb 06 2021 %t A138220 Select[Range[250],PrimeQ[900#^2+1]&] (* _Harvey P. Dale_, May 20 2012 *) %o A138220 (Magma) [n: n in [0..10000]| IsPrime(1+900*n^2)] // _Vincenzo Librandi_, Dec 13 2010 %o A138220 (PARI) is(n)=isprime(1+900*n^2) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A138220 Cf. A125251, A111175, A341183. %K A138220 nonn,easy %O A138220 1,1 %A A138220 _Zak Seidov_, May 05 2008