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A088499
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Doubly (3)-perfect numbers.
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27, 33, 45, 57, 69, 81, 105, 117, 141, 177, 189, 225, 249, 261, 285, 321, 357, 369, 405, 429, 441, 477, 501, 537, 585, 609, 621, 645, 657, 681, 765, 789, 825, 837, 897, 909, 945, 981, 1005, 1041, 1077, 1089, 1149, 1161, 1185, 1197, 1269, 1341, 1365, 1377
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| We define a doubly (r)-perfect number n as one for which Sum[d; 1<=d<n, n mod d=r] = 2n. It appears that all differences, a(n+1)-a(n), of consecutive (3)-perfect numbers are multiples of 6.
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EXAMPLE
| 27 is a (3)-perfect number since the integers d in 1..26 for which 27 mod d=3 are 4, 6, 8, 12 and 24 and these sum to 54=2*27.
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CROSSREFS
| Sequence in context: A024796 A025322 A151742 * A058902 A141550 A032584
Adjacent sequences: A088496 A088497 A088498 * A088500 A088501 A088502
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KEYWORD
| nonn
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AUTHOR
| John W. Layman (layman(AT)math.vt.edu), Nov 11 2003
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