id:A124197 - OEIS Search Results

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Number of subsets S of {1,2,3,...,n}, including the empty subset, such that if x and y are in S with x<>y and x+y even, then (x+y)/2 is also in S.

+0
1

2, 4, 7, 12, 18, 26, 36, 48, 61, 77, 95, 115, 137, 161, 187, 217, 248, 281, 317, 355, 395, 439, 485, 533, 583, 636, 691, 750, 811, 874, 941, 1010, 1080 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Conjecture. The second differences of this sequence give A001227, the number of odd divisors of n. (This is true for the 33 terms listed.)`
	CROSSREFS	`Cf. A001227.` `Sequence in context: A011910 A005521 A135901 this_sequence A011909 A065962 A049703` `Adjacent sequences: A124194 A124195 A124196 this_sequence A124198 A124199 A124200`
	KEYWORD	`nonn`
	AUTHOR	`John W. Layman (layman(AT)math.vt.edu), Dec 06 2006`

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Last modified December 4 12:22 EST 2008. Contains 151280 sequences.

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