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 A227007 #27 Jul 30 2025 19:27:49
%S A227007 2,3,4,7,8,15,22,43,44,87,130,259,302,603,904,1807
%N A227007 Numbers k such that k-1 is squarefree and every prime divisor of k-1 is in the sequence.
%C A227007 The complement of A227006.
%C A227007 1807 is the last term in this sequence. - _Charles R Greathouse IV_, Jun 27 2013
%H A227007 J. M. Grau, A. M. Oller-Marcén and J, Sondow, <a href="http://arxiv.org/abs/1309.7941">On the congruence 1^n+2^n+...+n^n == d (mod n), where d divides n</a>, arXiv preprint arXiv:1309.7941, 2013
%t A227007 Needs["NumberTheory`NumberTheoryFunctions`"];Is[2] = True; Is[{}] = True; Is[n_] := Is[n] = If[ListQ[n], Is[n[[1, 1]]] && Is[Rest[n]], SquareFreeQ[n - 1] && Is[fa[n - 1]]]; Select[1 + Range@10000, Is]
%Y A227007 Cf. A227006.
%K A227007 nonn,fini,full
%O A227007 1,1
%A A227007 _José María Grau Ribas_, Jun 27 2013