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

2,3

Comments

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

Links

Table of n, a(n) for n=2..42.

Index entries for sequences related to carryless arithmetic

Formula

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

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 *)

Crossrefs

Related to thickness: A169940-A169954, A061909.

Sequence in context: A244930 A130420 A214096 * A215110 A101715 A249751

Adjacent sequences: A169940 A169941 A169942 * A169944 A169945 A169946

Keyword

nonn

Author

N. J. A. Sloane, Aug 01 2010

Extensions

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

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

Status

approved