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 A083341 #29 Aug 24 2024 01:53:45 %S A083341 13,101,17,101,1344169,149,9049,37,710341,2122590346576634509, %T A083341 171707860473207588349837, %U A083341 7686544942807799800864250520468090636146175134909,2196283505473,598350346949,1211221552894876996541369232623365900407018851538797 %N A083341 Smaller factor of the n-th semiprime of the form (m!)^2 + 1. %H A083341 Hugo Pfoertner, <a href="/A083341/b083341.txt">Table of n, a(n) for n = 1..17</a> %H A083341 Andrew Walker, <a href="http://web.archive.org/web/20080808141339/http://www.uow.edu.au/~ajw01/ecm/pluspp.txt">Table of factors of (n!)^2+1</a>. %F A083341 Numbers p such that p*q = (A083340(n)!)^2 + 1, p, q prime, p < q. %e A083341 a(1) = 13 because (A083340(1)!)^2 + 1 = 518401 = 13*39877. %e A083341 a(15) = 1211221552894876996541369232623365900407018851538797 because (A083340(15)!)^2 + 1 = (55!)^2 + 1 can be factored into P52*P96 with a(15) = P52. %o A083341 (PARI) for(n=1,29,my(f=(n!)^2+1);if(bigomega(f)==2,print1(vecmin(factor(f)[,1]),", "))) \\ _Hugo Pfoertner_, Jul 13 2019 %Y A083341 Cf. A020549, A083340, subsequence of A282706. %K A083341 nonn,hard %O A083341 1,1 %A A083341 _Hugo Pfoertner_, Apr 25 2003 %E A083341 The 11th term of the sequence (49-digit factor of the 100-digit number (41!)^2+1) was found with Yuji Kida's multiple polynomial quadratic sieve UBASIC PPMPQS v3.5 in 13 days CPU time on an Intel PIII 550 MHz. %E A083341 Missing a(4) and new a(14), a(15) added by _Hugo Pfoertner_, Jul 13 2019