id:A130199 - OEIS Search Results

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Evil oblong (pronic) numbers.

+0
2

6, 12, 20, 30, 72, 90, 132, 156, 210, 240, 272, 306, 380, 420, 462, 600, 650, 756, 870, 1056, 1122, 1260, 1406, 1482, 1560, 1806, 1892, 1980, 2070, 2256, 2352, 2550, 2652, 3192, 3422, 3660, 3906, 4032, 4160, 4290, 4556, 4830, 5112, 5256, 5402, 5550, 5852 (list; graph; listen)

	OFFSET	`0,1`
	FORMULA	`a(n) = 2*A130200(n). Multiplying by 2 doesn't change evilness. Hence evil oblong numbers are twice evil triangular numbers.`
	EXAMPLE	`6 belongs to the sequence because binary expansion of 6 is 110 - contains an even number of ones.`
	MATHEMATICA	`Select[Table[n(n + 1), {n, 100}], EvenQ[Plus @@ IntegerDigits[ #, 2]] &]`
	CROSSREFS	`Cf. This sequence is the intersection of evil numbers (A001969) and oblong numbers (A002378).` `Sequence in context: A007622 A056930 A064971 this_sequence A117343 A028611 A141808` `Adjacent sequences: A130196 A130197 A130198 this_sequence A130200 A130201 A130202`
	KEYWORD	`nonn`
	AUTHOR	`Tanya Khovanova (tanyakh(AT)yahoo.com), May 16 2007`

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

AT&T Labs Research