id:A126779 - OEIS Search Results

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a(n) is equal to the number of functions f:{1,2,...,n}->{1,2,...,n} such that Im(f) contains 3 fixed elements.

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6, 60, 750, 11340, 201726, 4131036, 95750430, 2478397020, 70864914846, 2218385781612, 75463626886830, 2771883228523500, 109340261175108606, 4609962410815813308, 206883575626027168830, 9846362287666897852860 (list; graph; listen)

	OFFSET	`3,1`
	LINKS	`Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets`
	FORMULA	`a(n)=n^n-3(n-1)^n+3(n-2)^n-(n-3)^n, (n=3,4,...)`
	EXAMPLE	`a(7)=201726`
	MAPLE	`a:=n->n^n-3(n-1)^n+3(n-2)^n-(n-3)^n;`
	CROSSREFS	`Sequence in context: A000894 A112117 A065944 this_sequence A120973 A101470 A066151` `Adjacent sequences: A126776 A126777 A126778 this_sequence A126780 A126781 A126782`
	KEYWORD	`nonn`
	AUTHOR	`Aleksandar M. Janjic and Milan R. Janjic (agnus(AT)blic.net), Feb 18 2007`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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