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

Author

N. J. A. Sloane, Aug 01 2010

Keywords

• nonn

Comments

Wanted: a recurrence. Are any of A169940-A169954 related to any other entries in the OEIS?

Links

• Index entries for sequences related to carryless arithmetic

Crossrefs

Related to thickness: A169940-A169954, A061909.

Programs

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 *)

Formula

a(n) = A169953(n) - A169953(n-1) for n>2.

Extensions

a(15)-a(30) from Nathaniel Johnston, Nov 12 2010

a(31)-a(42) from Andrew Howroyd, Jul 09 2017