A104429 - OEIS

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A104429

Number of ways to split 1, 2, 3, ..., 3n into n arithmetic progressions each with 3 terms.

1, 1, 2, 5, 15, 55, 232, 1161, 6643, 44566, 327064, 2709050, 24312028, 240833770, 2546215687 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	REFERENCES	`R. J. Nowakowski, Generalizations of the Langford-Skolem problem, M.S. Thesis, Dept. Math., Univ. Calgary, May 1975. Gives a(0)-a(10). - N. J. Sloane, Dec 26 2011`
	EXAMPLE	`{{{1,2,3},{4,5,6},{7,8,9}}, {{1,2,3},{4,6,8},{5,7,9}}, {{1,3,5},{2,4,6},{7,8,9}}, {{1,4,7},{2,5,8},{3,6,9}}, {{1,5,9},{2,3,4},{6,7,8}}} are the 5 ways to split 1, 2, 3, ..., 9 into 3 arithmetic progressions each with 3 elements. Thus a(3)=5.`
	CROSSREFS	`Cf. A104430-A104443, A202705.` `Sequence in context: A171450 A051295 A009383 * A109319 A059219 A137533` `Adjacent sequences: A104426 A104427 A104428 * A104430 A104431 A104432`
	KEYWORD	`nonn,nice,more`
	AUTHOR	`Jonas Wallgren (jonwa(AT)ida.liu.se), Mar 17 2005`
	EXTENSIONS	`a(11)-a(14) from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Dec 28 2011`

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Last modified February 13 20:19 EST 2012. Contains 205553 sequences.