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 A320726 #27 Dec 14 2018 20:17:10 %S A320726 4,6,8,9,10,20,22,30,32,33,35,50,55,70,77,111 %N A320726 Composite numbers such that all other numbers obtained from all permutations of all subsets of the digits are noncomposite. %C A320726 Sequence is finite since it is a subsequence of a finite sequence (A071070). %C A320726 This is complete: there are only 16 terms in the sequence. %e A320726 371 is in this sequence because it's composite and none of the numbers 1, 3, 7, 13, 17, 31, 37, 137, 173, 317, 713 and 731 is composite. %t A320726 Select[Range[4, 10^3], Function[n, And[CompositeQ@ n, NoneTrue[DeleteCases[Flatten@ Map[If[Length@ # > 1, FromDigits /@ Permutations@ #, #] &, Rest@ Subsets@ IntegerDigits@ n], _?(# == n &)], CompositeQ]]]] (* _Michael De Vlieger_, Nov 13 2018 *) %Y A320726 Subsequence of A071070. Cf. A320725 (the same for prime numbers). %K A320726 nonn,base,fini,full %O A320726 1,1 %A A320726 _Daniel Lignon_, Oct 19 2018