A115866 a(n) = g(n,n,n) where g(a, b, c) is defined as follows: if a = 0 or b = 0 or c = 0 then return 1 otherwise return g(a, b, c-1) + g(a, b-1, c) + g(a-1, b, c) + g(a, b-1, c-1) + g(a-1, b, c-1) + g(a-1, b-1, c) + g(a-1, b-1, c-1).

1, 7, 157, 5419, 220561, 9763807, 454635973, 21894817147, 1080094827649, 54250971690007, 2763339510402637, 142338478909290187, 7399210542653679985, 387578046480606144079, 20433042381373273363477, 1083193405190852829195259, 57697563083258107660231681

Offset: 0

Author

Al Zimmermann, Apr 02 2006

Keywords

• nonn

Comments

A generalization of the recurrence in A001850. The original description of this sequence was the same as that of A126086. The correct explanation for these terms was provided by Nick Hobson, Mar 03 2007.

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..500

Crossrefs

Cf. A001850, A126086.

Column k=3 of A263159.

Programs

Maple

g():= seq(convert(n, base, 2)[1..3], n=9..15):
b:= proc(l) option remember;
      `if`(l[1]=0, 1, add(b(sort(l-h)), h=g()))
    end:
a:= n-> b([n$3]):
seq(a(n), n=0..25);  # Alois P. Heinz, Oct 14 2015

Mathematica

g[] = Table[Reverse[IntegerDigits[n, 2]][[;; 3]], {n, 2^3 + 1, 2^4 - 1}];
b[l_] := b[l] = If[l[[1]] == 0, 1, Sum[b[Sort[l - h]], {h, g[]}]];
a[n_] := b[Table[n, {3}]];
a /@ Range[0, 25] (* Jean-François Alcover, Apr 25 2020, after Alois P. Heinz *)

Formula

D-finite with recurrence: 2*(n-1)^2*(2*n-1)*(243*n^5 - 3159*n^4 + 16254*n^3 - 41325*n^2 + 51838*n - 25620)*a(n) = (53703*n^8 - 887922*n^7 + 6273882*n^6 - 24692601*n^5 + 59070956*n^4 - 87717383*n^3 + 78694087*n^2 - 38816698*n + 8003688)*a(n-1) + (94527*n^8 - 1549611*n^7 + 10848681*n^6 - 42278007*n^5 + 100087538*n^4 - 147021644*n^3 + 130465402*n^2 - 63678226*n + 13003980)*a(n-2) - (31833*n^8 - 541890*n^7 + 3945213*n^6 - 16007835*n^5 + 39486422*n^4 - 60435299*n^3 + 55812796*n^2 - 28273516*n + 5965068)*a(n-3) + (n-3)*(3159*n^7 - 48114*n^6 + 301212*n^5 - 1002003*n^4 + 1908157*n^3 - 2073535*n^2 + 1184960*n - 272792)*a(n-4) - 2*(n-4)^2*(n-3)*(243*n^5 - 1944*n^4 + 6048*n^3 - 9087*n^2 + 6529*n - 1769)*a(n-5). - Vaclav Kotesovec, Nov 27 2016

a(n) ~ (12*2^(2/3)+15*2^(1/3)+19)^n / (2^(4/3)*3^(1/2)*Pi*n). - Vaclav Kotesovec, Nov 27 2016

Extensions

Edited by N. J. A. Sloane following email from Nick Hobson, Mar 03 2007

More terms from Alois P. Heinz, Sep 30 2015