%I #21 Apr 06 2015 15:16:23
%S 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 25,25,29,29,29,29,29,29,29,29,29,29,29,40,41,42,43,44,45,46,47,48,49,
%U 50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67
%N a(n) = smallest missing number after seeing A166133(n).
%C The distinct terms are listed in A256408. See also A256409.
%C See the "blog" file in A166133 for discussion.
%H Reinhard Zumkeller, <a href="/A256405/b256405.txt">Table of n, a(n) for n = 1..10000</a>
%H John Mason, <a href="/A256405/a256405.txt">Table of n, a(n) for n = 1..722392</a> [10 megabytes]
%H John Mason, <a href="/A256405/a256405_1.txt">Table of n, a(n) for n = 1..2000000</a> [31 megabytes]
%H John Mason, <a href="https://oeis.org/A256405/a256405-10M.zip">Ten million terms (zipped file)</a>
%o (Haskell)
%o import Data.List (delete); import Data.List.Ordered (isect)
%o a256405 n = a256405_list !! (n-1)
%o a256405_list = 2 : 3 : f (3:[5..]) 4 where
%o f zs@(z:_) x = z : f (delete y zs) y where
%o y = head $ isect (a027750_row' (x ^ 2 - 1)) zs
%o -- _Reinhard Zumkeller_, Apr 01 2015
%Y Cf. A166133, A027750, A005563, A256408, A256409.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Apr 01 2015