|
%I #17 Apr 30 2014 01:34:22
%S 1,2,4,4,1
%N Number of distinct n-row absolute difference tables that consist entirely of the first A000217(n) natural numbers.
%C Mirror image triangle pairs are consider the same.
%D M. Gardner, "Pool-Ball Triangles", pp. 119-120 and 128, Penrose Tiles to Trapdoor Ciphers, Freeman NY 1989.
%D M. Gardner, Puzzles From Other Worlds, Problem 8, pp. 143; 173, Random House NY 1984.
%D J. D. E. Konhauser et al., " Difference triangles", Problem 145, pp. 43; 184-6, Which Way Did The Bicycle Go, MAA 1996.
%D P. Tougne, " Jeux Mathematiques", Aug. 1982 issue of Pour La Science (French edition of 'Scientific American'), Paris.
%H D. Greenwell, <a href="http://math2.eku.edu/greenwell/mat303/triangles/">Pool-ball Triangles</a>.
%H T. Sillke, <a href="http://www.mathematik.uni-bielefeld.de/~sillke/PUZZLES/triangle-abs-diff">Absolute-difference triangles</a>
%e Illustrating the case of the unique example of n=5 with numbers 1 through 15:
%e 6..14.15..3..13
%e ..8..1..12.10
%e ...7..11..2
%e ....4...9
%e ......5
%e For n=2 we have 1,3;2 and 2,3;1 so a(2) = 2. - _Michael Somos_, Apr 07 2012
%K nonn,fini
%O 1,2
%A _Lekraj Beedassy_, May 28 2004
|
