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 A309747 #12 Aug 18 2019 16:45:33 %S A309747 5,7,9,11,14,21,37,38,39,57,90,97,162 %N A309747 Numbers k such that k^k + (k+1)^(k+1) is a semiprime. %C A309747 Numbers k such that A217435(k+1) = 2. %C A309747 a(14) >= 235, see FactorDB link. %H A309747 FactorDB, <a href="http://factordb.com/index.php?query=236%5E236%2B235%5E235">Status of 235^235+236^236</a>. %H A309747 Walter Nissen, <a href="http://upforthecount.com/math/nnp2.txt">Addendum to Prime factors of n^n + (n+1)^(n+1)</a>, Table F, 2014-01-07. %e A309747 a(1) = 5 because 5^5 + 6^6 = 49781 = 67*743. %o A309747 (PARI) for(k=0,40,if(bigomega(k^k+(k+1)^(k+1))==2,print1(k,", "))) %Y A309747 Cf. A056187, A056788, A056790, A217435. %K A309747 nonn,more,hard %O A309747 1,1 %A A309747 _Hugo Pfoertner_, Aug 15 2019