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A195437 Triangle formed by: 1 even, 2 odd, 3 even, 4 odd... starting with 2.

%I A195437 #21 Aug 27 2023 12:13:25
%S A195437 2,5,7,10,12,14,17,19,21,23,26,28,30,32,34,37,39,41,43,45,47,50,52,54,
%T A195437 56,58,60,62,65,67,69,71,73,75,77,79,82,84,86,88,90,92,94,96,98,101,
%U A195437 103,105,107,109,111,113,115,117,119,122,124,126,128,130,132
%N A195437 Triangle formed by: 1 even, 2 odd, 3 even, 4 odd... starting with 2.
%C A195437 A127366(T(n,k)) mod 2 = 1;
%C A195437 T(n,k) mod 2 + A000196(T(n,k)) mod 2 = 1;
%C A195437 complement of A133280.
%H A195437 Reinhard Zumkeller, <a href="/A195437/b195437.txt">Rows n=0..100 of triangle, flattened</a>
%t A195437 p[n_,k_]:=NestList[#+2&,n,k-1]; Module[{nn=6,ev,od},ev=p@@@Partition[Riffle[Table[ 4n^2-4n+2,{n,nn}],Range[ 1,2nn,2]],2];od=p@@@Partition[Riffle[Table[4n^2+1,{n,nn}],Range[ 2,2nn+1,2]],2];Sort[Flatten[Join[ev,od]]]] (* _Harvey P. Dale_, Aug 27 2023 *)
%o A195437 (Haskell)
%o A195437 a195437 n k = a195437_tabl !! n !! k
%o A195437 a195437_tabl = tail $ g 1 1 [0..] where
%o A195437    g m j xs = (filter ((== m) . (`mod` 2)) ys) : g (1 - m) (j + 2) xs'
%o A195437      where (ys,xs') = splitAt j xs
%o A195437 b195437 = bFile' "A195437" (concat $ take 101 a195437_tabl) 0
%o A195437 -- _Reinhard Zumkeller_, Nov 23 2011 (fixed), Oct 12 2011
%Y A195437 Cf. A002522 (left edge), A008865 (right edge), A011379 (row sums), A002939 (central terms).
%K A195437 nonn,tabl
%O A195437 0,1
%A A195437 _Reinhard Zumkeller_, Oct 12 2011