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 A251392 #8 Jul 11 2024 07:15:20 %S A251392 1,4,5,6,7,8,10,11,12,13,14,16,17,18,19,20,21,24,25,26,27,28,29,31,32, %T A251392 33,34,35,36,37,38,39,40,41,42,44,45,46,47,48,49,50,52,53,54,55,56,57, %U A251392 58,59,60,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77 %N A251392 Indices of nonprimes in A098550. %C A251392 A010051(A098550(a(n))) = 0; A239968(A098550(a(n))) > 0; %C A251392 three equivalent statements: %C A251392 1) A098550 is a permutation of the positive integers, cf. A000027; %C A251392 2) A251392 is a permutation of the nonprimes, cf. A018252; %C A251392 3) A251392 is the complement of A251239. %H A251392 Reinhard Zumkeller, <a href="/A251392/b251392.txt">Table of n, a(n) for n = 1..10000</a> %o A251392 (Haskell) %o A251392 a251392 n = a251392_list !! (n-1) %o A251392 a251392_list = filter ((== 0) . a010051' . a098550) [1..] %Y A251392 Cf. A098550, A018252, A010051, A239968, A251239, A251240 (subsequence). %K A251392 nonn %O A251392 1,2 %A A251392 _Reinhard Zumkeller_, Dec 03 2014