id:A117284 - OEIS Search Results

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Numbers n for which the cototient n-phi(n) is a triangular number.

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1, 2, 3, 5, 7, 9, 10, 11, 13, 17, 19, 23, 29, 31, 37, 39, 41, 43, 45, 47, 52, 53, 54, 55, 57, 59, 61, 67, 68, 71, 73, 79, 83, 85, 89, 90, 97, 101, 103, 107, 109, 113, 114, 117, 127, 129, 131, 137, 139, 149, 151, 157, 159, 163, 167, 168, 173, 175, 179, 181, 191, 193 (list; graph; listen)

	OFFSET	`0,2`
	EXAMPLE	`39 is in the sequence because 39-phi(39)=15, which is a triangular number.`
	CROSSREFS	`Cf. A000217.` `Sequence in context: A047489 A035061 A096738 this_sequence A137377 A026277 A076355` `Adjacent sequences: A117281 A117282 A117283 this_sequence A117285 A117286 A117287`
	KEYWORD	`nonn`
	AUTHOR	`Luc Stevens (lms022(AT)yahoo.com), Apr 23 2006`

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.

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