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 A308339 #14 Jun 01 2019 10:14:58 %S A308339 21,30,49,51,75,82,96,106,120,130,133,136,141,148,152,157,161,173,177, %T A308339 180,186,187,189,202,207,209,213,217,221,226,236,240,242,244,248,261, %U A308339 264,277,285,286,294,305,306,311,317,320,322,327,333,349,355,364,368 %N A308339 Sphenic number indices of A215217. %C A308339 A215217 is a subsequence of A007304 (by definition). The index sequence is more compact. %H A308339 Peter Dolland, <a href="/A308339/b308339.txt">Table of n, a(n) for n = 1..200</a> %F A308339 A215217(n) = A007304(a(n)). %e A308339 For n = 3: a(3) = 49 and A215217(3) = 429 = A007304(49). %o A308339 (Haskell) %o A308339 twinLowX [] = [] %o A308339 twinLowX [_] = [] %o A308339 twinLowX (n : (m : ns)) %o A308339 | m == n + 1 = 1 : (map succ (twinLowX (m : ns))) %o A308339 | otherwise = (map succ (twinLowX (m : ns))) %o A308339 a308339 n = (twinLowX a007304_list) !! (n - 1) %o A308339 -- _Peter Dolland_, May 31 2019 %Y A308339 Cf. A007304, A215217. %K A308339 nonn %O A308339 1,1 %A A308339 _Peter Dolland_, May 20 2019