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A094225 Number of distinct n-row absolute difference tables that consist entirely of the first A000217(n) natural numbers. 0
1, 2, 4, 4, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Mirror image triangle pairs are consider the same.

REFERENCES

M. Gardner, "Pool-Ball Triangles", pp. 119-120 and 128, Penrose Tiles to Trapdoor Ciphers, Freeman NY 1989.

M. Gardner, Puzzles From Other Worlds, Problem 8, pp. 143; 173, Random House NY 1984.

J. D. E. Konhauser et al., " Difference triangles", Problem 145, pp. 43; 184-6, Which Way Did The Bicycle Go, MAA 1996.

P. Tougne, " Jeux Mathematiques", Aug. 1982 issue of Pour La Science (French edition of 'Scientific American'), Paris.

LINKS

Table of n, a(n) for n=1..5.

D. Greenwell, Pool-ball Triangles.

T. Sillke, Absolute-difference triangles

EXAMPLE

Illustrating the case of the unique example of n=5 with numbers 1 through 15:

6..14.15..3..13

..8..1..12.10

...7..11..2

....4...9

......5

For n=2 we have 1,3;2 and 2,3;1 so a(2) = 2. - Michael Somos, Apr 07 2012

CROSSREFS

Sequence in context: A099211 A261761 A300269 * A057277 A258712 A238094

Adjacent sequences:  A094222 A094223 A094224 * A094226 A094227 A094228

KEYWORD

nonn,fini

AUTHOR

Lekraj Beedassy, May 28 2004

STATUS

approved

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Last modified October 20 07:17 EDT 2018. Contains 316378 sequences. (Running on oeis4.)