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 A256405 #21 Apr 06 2015 15:16:23 %S A256405 2,3,3,5,5,5,5,9,9,9,9,13,13,13,13,17,17,17,17,17,22,22,22,25,25,25, %T A256405 25,25,29,29,29,29,29,29,29,29,29,29,29,40,41,42,43,44,45,46,47,48,49, %U A256405 50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67 %N A256405 a(n) = smallest missing number after seeing A166133(n). %C A256405 The distinct terms are listed in A256408. See also A256409. %C A256405 See the "blog" file in A166133 for discussion. %H A256405 Reinhard Zumkeller, <a href="/A256405/b256405.txt">Table of n, a(n) for n = 1..10000</a> %H A256405 John Mason, <a href="/A256405/a256405.txt">Table of n, a(n) for n = 1..722392</a> [10 megabytes] %H A256405 John Mason, <a href="/A256405/a256405_1.txt">Table of n, a(n) for n = 1..2000000</a> [31 megabytes] %H A256405 John Mason, <a href="https://oeis.org/A256405/a256405-10M.zip">Ten million terms (zipped file)</a> %o A256405 (Haskell) %o A256405 import Data.List (delete); import Data.List.Ordered (isect) %o A256405 a256405 n = a256405_list !! (n-1) %o A256405 a256405_list = 2 : 3 : f (3:[5..]) 4 where %o A256405 f zs@(z:_) x = z : f (delete y zs) y where %o A256405 y = head $ isect (a027750_row' (x ^ 2 - 1)) zs %o A256405 -- _Reinhard Zumkeller_, Apr 01 2015 %Y A256405 Cf. A166133, A027750, A005563, A256408, A256409. %K A256405 nonn %O A256405 1,1 %A A256405 _N. J. A. Sloane_, Apr 01 2015