A169943 - OEIS

%I #14 Oct 10 2017 15:33:03

%S 1,0,3,4,7,8,21,20,53,56,89,112,197,220,397,456,711,850,1347,1428,

%T 2303,2642,3777,4636,6693,7550,11109,12876,17965,21000,29207,32952,

%U 46263,53372,71069,82660,111877,126042,172461,195898,256577

%N Second entry in row n of triangle in A169940.

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

%H <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>

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

%t (* 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 *)

%Y Related to thickness: A169940-A169954, A061909.

%K nonn

%O 2,3

%A _N. J. A. Sloane_, Aug 01 2010

%E a(15)-a(30) from _Nathaniel Johnston_, Nov 12 2010

%E a(31)-a(42) from _Andrew Howroyd_, Jul 09 2017