id:A131651 - OEIS Search Results

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Positive integers obtained as the difference of two triangular numbers in exactly 4 ways.

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15, 21, 27, 30, 33, 35, 39, 42, 51, 54, 55, 57, 60, 65, 66, 69, 70, 77, 78, 84, 85, 87, 91, 93, 95, 102, 108, 110, 111, 114, 115, 119, 120, 123, 125, 129, 130, 132, 133, 138, 140, 141, 143, 145, 154, 155, 156, 159, 161, 168, 170, 174, 177, 182, 183, 185, 186, 187 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`It appears that terms of the sequence are all given by a power of 2 times the cube of an odd prime or a power of 2 times a product of two distinct odd primes. (This has been verified for a(n)<=10000.)`
	CROSSREFS	`Cf. A001227, A038550, A072502.` `Sequence in context: A057489 A070811 A138594 this_sequence A134642 A072974 A082686` `Adjacent sequences: A131648 A131649 A131650 this_sequence A131652 A131653 A131654`
	KEYWORD	`nonn`
	AUTHOR	`John W. Layman (layman(AT)math.vt.edu), Sep 10 2007`

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

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