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 A053609 #9 Aug 23 2024 08:42:05 %S A053609 2,5,37,176401,129859329601, %T A053609 516625648014869290354797521879383114125823989794742396526049715541246671360001 %N A053609 Primes of form x^2+1 where x = LCM(1,2,...,k) for some k. %C A053609 The next term has k > 10^4, if it exists. - _Amiram Eldar_, Aug 23 2024 %F A053609 a(n) = A053608(A053608(n)) = A053608(n)^2 + 1. - _Amiram Eldar_, Aug 23 2024 %t A053609 Select[FoldList[LCM, 1, Select[Range[100], PrimePowerQ]]^2 + 1, PrimeQ] (* _Amiram Eldar_, Aug 23 2024 *) %Y A053609 Cf. A049536, A046029, A051739, A051418, A051451, A053608. %K A053609 nonn,hard %O A053609 1,1 %A A053609 _Labos Elemer_, Feb 09 2000