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 A387613 #8 Sep 04 2025 14:55:31 %S A387613 1,3,6,9,11,12,14,18,22,24,26,29,31,32,41,42,44,45,47,49,50,52,55,57, %T A387613 58,68,70,71,73,74,76,77,98,101,102,104,109,113,115,119,122,123,124, %U A387613 126,137,138,142,144,174,179,187,189,192,193,196,203,205,207,234 %N A387613 Numbers k such that A386482(k) and A386482(k+2) are coprime. %C A387613 For k > 1, A386482(k) and A386482(k+1) share a prime factor, however A386482(k) and A386482(k+2) may not share a prime factor. The present sequence lists those indexes. %H A387613 Rémy Sigrist, <a href="/A387613/b387613.txt">Table of n, a(n) for n = 1..10000</a> %H A387613 Rémy Sigrist, <a href="/A387613/a387613.gp.txt">PARI program</a> %e A387613 The first terms, alongside the first terms of A386482, are: %e A387613 k A386482(k) A386482(k+2) n a(n) %e A387613 -- ---------- ------------ -- ---- %e A387613 1 1 4 1 1 %e A387613 2 2 6 %e A387613 3 4 3 2 3 %e A387613 4 6 9 %e A387613 5 3 12 %e A387613 6 9 10 3 6 %e A387613 7 12 8 %e A387613 8 10 14 %e A387613 9 8 7 4 9 %e A387613 10 14 21 %e A387613 11 7 18 5 11 %e A387613 12 21 16 6 12 %e A387613 13 18 20 %e A387613 14 16 15 7 14 %e A387613 15 20 5 %o A387613 (PARI) \\ See Links section. %Y A387613 Cf. A386482, A387087. %K A387613 nonn,new %O A387613 1,2 %A A387613 _Rémy Sigrist_, Sep 03 2025