id:A133033 - OEIS Search Results

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Number of proper divisors of n-th perfect number.

+0
10

3, 5, 9, 13, 25, 33, 37, 61, 121, 177, 213, 253, 1041, 1213, 2557, 4405, 4561, 6433, 8505, 8845, 19377, 19881, 22425, 39873, 43401, 46417, 88993, 172485, 221005, 264097, 432181, 1513677, 1718865, 2515573, 2796537, 5952441, 6042753, 13945185 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Perfect numbers: A000396(n) = 2^a(n) - 2^A090748(n).` `Also, a(n) is equal to the number of bits in A135650(n), the n-th perfect number A000396(n) written in base 2.`
	LINKS	`C. K. Caldwell, "Top Twenty" page, Mersenne Primes.` `O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.`
	FORMULA	`a(n) = A061645(n) - 1; a(n) = A000043(n) + A090748(n); a(n) = 2 * A000043(n) - 1; a(n) = 2 * A090748(n) + 1.`
	CROSSREFS	`Cf. A135650.` `Sequence in context: A136252 A052282 A001993 this_sequence A134672 A082874 A127720` `Adjacent sequences: A133030 A133031 A133032 this_sequence A133034 A133035 A133036`
	KEYWORD	`nonn`
	AUTHOR	`Omar E. Pol (info(AT)polprimos.com), Oct 27 2007, Feb 23 2008`

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Last modified July 23 17:35 EDT 2008. Contains 142285 sequences.

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