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 A176658 #8 Feb 07 2019 02:14:27
%S A176658 3,5,11,14,20,32,52,57,70,72,81,95,114,124,231,240,273,276,287,291,
%T A176658 371,380,441,507,528,544,573,607,629,647,672,695,716,739,828,830,832,
%U A176658 873,1002,1035,1037,1044,1100,1104,1182,1208,1236,1278,1321,1340,1367,1522
%N A176658 Numbers k such that semiprime(semiprime(k)) + 1 = semiprime(semiprime(k+1)).
%C A176658 Numbers k such that A001358(A001358(k)) + 1 = A001358(A001358(k+1)).
%C A176658 Numbers k such that A091022(k) + 1 = A091022(k+1).
%e A176658 3 is a term because semiprime(semiprime(3)) + 1 = 25 + 1 = semiprime(semiprime(3+1)).
%p A176658 A091022 := proc(n) A001358(A001358(n)) ; end proc: isA176658 := proc(n) A091022(n)+1 = A091022(n+1) ; end proc: for n from 1 to 1600 do if isA176658(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Apr 26 2010
%Y A176658 Cf. A001358, A091022.
%K A176658 nonn
%O A176658 1,1
%A A176658 _Juri-Stepan Gerasimov_, Apr 23 2010
%E A176658 Corrected (72 inserted, 85 replaced by 95, 124 inserted) and extended by _R. J. Mathar_, Apr 26 2010