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 A188549 #21 Aug 03 2025 00:05:54 %S A188549 3,12,15,18,21,33,36,48,51,66,78,81,93,102,114,120,132,150,153,162, %T A188549 180,183,213,225,228,231,234,237,243,246,252,279,282,285,294,303,318, %U A188549 324,333,375,378,381,384,393,396,399,417,432,450,459,468,480,489,495,510 %N A188549 Numbers k such that 8*k^2+1 is a prime. %C A188549 Half of the even terms of A089001. - _R. J. Mathar_, Apr 09 2011 %H A188549 Vincenzo Librandi, <a href="/A188549/b188549.txt">Table of n, a(n) for n = 1..1000</a> %t A188549 Select[Range[600],PrimeQ[8#^2+1]&] (* _Harvey P. Dale_, Apr 11 2012 *) %o A188549 (Magma) [n: n in [1..1800]|IsPrime(8*n^2 + 1)]; // _Vincenzo Librandi_, Apr 04 2011 %Y A188549 Cf. A090685 (Primes of the form 8*n^2 + 1), A089001. %K A188549 nonn,easy %O A188549 1,1 %A A188549 _Vincenzo Librandi_, Apr 04 2011