id:A073040 - OEIS Search Results

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Numbers n such that sum of divisors of n, sigma (n), minus n is a perfect square.

+0
2

1, 2, 3, 5, 7, 9, 11, 12, 13, 15, 17, 19, 23, 24, 26, 29, 31, 37, 41, 43, 47, 53, 56, 59, 61, 67, 71, 73, 75, 76, 79, 83, 89, 90, 95, 97, 101, 103, 107, 109, 113, 119, 122, 124, 127, 131, 137, 139, 140, 143, 147, 149, 151, 153, 157, 163, 167, 173, 176, 179, 181, 191, 193, 194 (list; graph; listen)

	OFFSET	`1,2`
	MAPLE	`with(numtheory); a := []; for n from 1 to 2000 do if issqr(sigma(n)-n) then a := [op(a), n]; fi; od: a;`
	CROSSREFS	`Cf. A048698.` `Sequence in context: A155498 A069149 A042996 this_sequence A087268 A106765 A061979` `Adjacent sequences: A073037 A073038 A073039 this_sequence A073041 A073042 A073043`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), Aug 24 2002`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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