A128816 - OEIS

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A128816

Number of partitions of an n-element set avoiding the pattern 12|3.

1, 1, 2, 4, 8, 19, 53, 160, 512, 1753, 6431, 25072, 103022, 444145, 2004281, 9447784, 46407476, 236950873, 1254862955, 6880495528, 38999582018, 228195894313, 1376543144453, 8550048509440, 54619642413848 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,3`
	LINKS	`A. M. Goyt, Avoidance of partitions of a 3-element set`
	FORMULA	`a(0)=1, a(1)=1, a(n) = 1 + a(n-1) + sum(k=1,n-2, C(n-2,k)*a(n-k-2) ).` `The e.g.f. satisfies the diff.eq. y''=y'+y(e^x-1)+e^x.`
	CROSSREFS	`Sequence in context: A100133 A099598 A173310 * A006897 A034767 A005518` `Adjacent sequences: A128813 A128814 A128815 * A128817 A128818 A128819`
	KEYWORD	`nonn`
	AUTHOR	`Ralf Stephan, May 08 2007`

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Last modified February 15 03:33 EST 2012. Contains 205694 sequences.