id:A113930 - OEIS Search Results

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Numbers n such that sigma(n) and phi(n) are both triangular numbers.

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1, 2, 22, 3051, 3219, 3393, 5057, 8653, 75618, 95675, 100503, 102949, 104714, 287826, 438547, 522339, 537159, 688050, 2191200, 2317118, 2418548, 2507683, 2599128, 3212964, 4534573, 5367797, 6047913, 6302639, 7689149 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`phi(n)=A000010(n) is the Euler totient function, while sigma(n)=A000203(n) is the sum of divisors of n`
	EXAMPLE	`sigma(100503)=156520=T(559) and phi(100503)=61776=T(351).`
	CROSSREFS	`Cf. A000010, A000203.` `Adjacent sequences: A113927 A113928 A113929 this_sequence A113931 A113932 A113933` `Sequence in context: A054948 A113761 A054349 this_sequence A060601 A053952 A052077`
	KEYWORD	`nonn`
	AUTHOR	`Giovanni Resta (g.resta(AT)iit.cnr.it), Jan 30 2006`

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Last modified October 11 13:47 EDT 2008. Contains 144830 sequences.

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