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Number of ways to arrange 5 indistinguishable points on an n X n X n triangular grid so that no three points are in the same row or diagonal.
1

%I #12 May 05 2018 08:06:41

%S 0,0,0,39,909,8568,50526,221508,789453,2412333,6542316,16127397,

%T 36762726,78495417,158548572,305303544,563965038,1004432454,

%U 1732013856,2901747051,4737236427,7555075374,11796103242,18064943820,27179490195,40232239515

%N Number of ways to arrange 5 indistinguishable points on an n X n X n triangular grid so that no three points are in the same row or diagonal.

%C Column 5 of A194480.

%H R. H. Hardin, <a href="/A194477/b194477.txt">Table of n, a(n) for n = 1..47</a>

%F Empirical: a(n) = (1/3840)*n^10 + (1/768)*n^9 - (7/384)*n^8 + (37/1920)*n^7 + (737/3840)*n^6 - (2347/3840)*n^5 + (101/192)*n^4 + (93/320)*n^3 - (7/10)*n^2 + (3/10)*n.

%F Empirical g.f.: 3*x^4*(13 + 160*x + 238*x^2 - 54*x^3 - 51*x^4 + 9*x^5) / (1 - x)^11. - _Colin Barker_, May 05 2018

%e Some solutions for 4 X 4 X 4:

%e .....0........0........0........0........0........1........1........0

%e ....0.1......0.1......1.0......1.0......1.0......0.0......1.0......0.1

%e ...1.1.0....1.0.1....1.0.1....0.1.1....1.0.1....1.0.1....0.1.0....1.0.1

%e ..0.0.1.1..0.1.1.0..0.1.1.0..1.1.0.0..0.1.0.1..0.1.1.0..0.1.0.1..1.1.0.0

%Y Cf. A194480.

%K nonn

%O 1,4

%A _R. H. Hardin_, Aug 26 2011

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Last modified September 19 20:04 EDT 2024. Contains 376014 sequences. (Running on oeis4.)