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A169943 Second entry in row n of triangle in A169940. 0
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 (list; graph; refs; listen; history; text; internal format)
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-Fran├žois 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

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Last modified January 25 01:33 EST 2020. Contains 331229 sequences. (Running on oeis4.)