id:A112951 - OEIS Search Results

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Number of indecomposable Schur rings over the field Z_{2^n}.

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1, 2, 5, 16, 63, 271, 1225, 5726, 27461, 134461, 669795, 3384945, 17316771, 89518347, 466932059, 2454546192, 12990743783, 69164599115, 370186756425, 1990638982239, 10749412063853, 58265968105385, 316903203993921 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Counts also special lattice paths combining ones enumerated by the Catalan numbers A000108 and the large Schroeder numbers A006318.`
	LINKS	`I. Kov\'acs, The number of indecomposable Schur rings over a cyclic 2-group,S\'eminaire Lotharingien de Combinatoire, vol. 51 (2005), Article B51h.`
	FORMULA	`G.f.: 2/(3x+sqrt(1-4x)+sqrt(1-6x+x^2))+x/(1-x).`
	CROSSREFS	`Cf. A000108, A006318.` `Adjacent sequences: A112948 A112949 A112950 this_sequence A112952 A112953 A112954` `Sequence in context: A138549 A058117 A007124 this_sequence A124470 A105072 A022494`
	KEYWORD	`nonn`
	AUTHOR	`Valery A. Liskovets (liskov(AT)im.bas-net.by), Oct 10 2005`

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Last modified October 11 13:47 EDT 2008. Contains 144830 sequences.

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