id:A068983 - OEIS Search Results

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Sigma(k^k-k!).

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0, 2, 23, 255, 3260, 49196, 867699, 17604595, 404662204, 10401033404, 295672787215, 9211294233871, 312080173805324, 11423999821072140, 449316582527563515, 18896039733447227131, 846135945932355895308 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`a(n)=# non-injective functions [k]->[k] for 1<=k<=n`
	FORMULA	`a(n)=sigma(k^k-k!) for k = 1 to n`
	EXAMPLE	`a(4)=255 because (1^1-1!)+(2^2-2!)+(3^3-3!)+(4^4-4!)=255`
	CROSSREFS	`Cf. A036679.` `Sequence in context: A110773 A088087 A088085 this_sequence A083427 A083470 A064110` `Adjacent sequences: A068980 A068981 A068982 this_sequence A068984 A068985 A068986`
	KEYWORD	`easy,nonn`
	AUTHOR	`Darrell Minor (dminor(AT)cscc.edu), Apr 02 2002`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

AT&T Labs Research