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Infinite sequence gradually builds a triangle plus another more widely spaced triangle on top of it, or overlapping, if you will.
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%I #11 Dec 02 2019 09:24:44

%S 2,2,2,2,3,3,4,5,5,6,7,8,9,10,11,12,14,15,16,18,19,21,23,24,26,28,30,

%T 32,34,36,38,41,43,45,48,50,53,56,58,61,64,67,70,73,76,79,83,86,89,93,

%U 96,100,104,107,111,115,119,123,127,131,135,140,144,148,153,157,162,167

%N Infinite sequence gradually builds a triangle plus another more widely spaced triangle on top of it, or overlapping, if you will.

%C This sequence almost builds a square (two triangles with the sparse triangle rotated), but not quite.

%H Eric Werner, <a href="/A173777/b173777.txt">Table of n, a(n) for n = 1..311</a>

%F Conjectures from _Colin Barker_, Dec 01 2019: (Start)

%F G.f.: x*(2 - 2*x^3 + x^4 - 2*x^5 + x^6 + 2*x^8 - x^9) / ((1 - x)^3*(1 + x + x^2)*(1 + x + x^2 + x^3 + x^4)).

%F a(n) = a(n-1) + a(n-3) - a(n-4) + a(n-5) - a(n-6) - a(n-8) + a(n-9) for n>10.

%F (End)

%K nonn,obsc,uned

%O 1,1

%A Eric Werner (eric.werner(AT)gmx.net), Feb 24 2010