A169943 Second entry in row n of triangle in A169940.
1, 0, 3, 4, 7, 8, 21, 20, 53, 56, 89, 112, 197, 220, 397, 456, 711, 850, 1347, 1428, 2303, 2642, 3777, 4636, 6693, 7550, 11109, 12876, 17965, 21000, 29207, 32952, 46263, 53372, 71069, 82660, 111877, 126042, 172461, 195898, 256577
Offset: 2
Keywords
Programs
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Mathematica
(* Very slow *) a[n_] := Module[{dd, xx, mm}, dd = Join[{1}, PadLeft[ IntegerDigits[#, 2], n - 1], {1}] & /@ Range[0, 2^(n - 1) - 1]; xx = (((x^Range[n, 0, -1]).#) & /@ dd)^2 // Expand; mm = Max[ CoefficientList[ #, x]] & /@ xx; Count[mm, 3]]; Table[an = a[n]; Print["a(", n, ") = ", an]; an, {n, 2, 20}] (* Jean-François Alcover, Oct 10 2017 *)
Extensions
a(15)-a(30) from Nathaniel Johnston, Nov 12 2010
a(31)-a(42) from Andrew Howroyd, Jul 09 2017
Comments