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 A087552 #14 Jul 30 2022 09:37:09 %S A087552 1,2,11,5,3,29,101,113,41,271,7,13,239,613,73,137,37,8291,9091,157637, %T A087552 313,21649,9901,2733970560857,53,79,229,4649,31,13001,17,19,6529, %U A087552 664193,6781,52579,1111111111111111111 %N A087552 a(1) = 1, then the smallest prime divisor of A065447(n) not included earlier. %C A087552 Conjecture: Every prime is a member and this is a rearrangement of the noncomposite numbers. %C A087552 Proof of conjecture: primes 2=a(1) and 5=a(3) are terms, while any other prime divides infinitely many numbers of the form A002275([(n+1)/2]) = (10^[(n+1)/2]-1)/9, which in turn divide A065447(n). Thus every prime will sooner or later appear as a(n). - _Max Alekseyev_, Jul 03 2019 %e A087552 a(6) = 29; smallest prime divisor of 100111000011111000000 not included earlier is 29. The prime divisors are 2, 3, 5, 29, 37, 97 and 106872959. %Y A087552 Cf. A002275, A065447. %K A087552 base,more,nonn %O A087552 1,2 %A A087552 _Amarnath Murthy_, Sep 13 2003 %E A087552 More terms from _David Wasserman_, Jun 06 2005 %E A087552 Offset corrected by _Max Alekseyev_, Jul 03 2019