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A249406 Start with a(1) = 1, and extend by the rule that the next term is the product of the two most recent non-terms of the sequence.

%I A249406 #18 May 09 2021 02:51:53
%S A249406 1,6,20,56,90,132,182,240,306,399,506,600,702,812,930,1056,1190,1332,
%T A249406 1482,1640,1806,1980,2162,2352,2550,2756,2970,3306,3540,3782,4032,
%U A249406 4290,4556,4830,5112,5402,5700,6006,6320,6642,6972,7310,7656,8099,8556,8930,9312
%N A249406 Start with a(1) = 1, and extend by the rule that the next term is the product of the two most recent non-terms of the sequence.
%C A249406 Compare to A075326, where not products, but sums of the two most recent non-terms are considered;
%C A249406 a(195) = 159200 is the smallest even term not of the form m*(m+1); see also A249408, the set of all non-oblong terms of this sequence.
%C A249406 a(10) = 399 is the smallest odd term.
%H A249406 Reinhard Zumkeller, <a href="/A249406/b249406.txt">Table of n, a(n) for n = 1..10000</a>
%o A249406 (Haskell)
%o A249406 import Data.List ((\\))
%o A249406 a249406 n = a249406_list !! (n-1)
%o A249406 a249406_list = 1 : f [2..] where
%o A249406    f ws@(u:v:_) = y : f (ws \\ [u, v, y]) where y = u * v
%Y A249406 Cf. A000301, A000304, A075326, A249055, A249407 (complement), subsequence of A002808.
%K A249406 nonn
%O A249406 1,2
%A A249406 _Reinhard Zumkeller_, Oct 31 2014