| 1, 3, 7, 13, 15, 31, 39, 57, 63, 91, 93, 121, 127, 133, 171, 183, 195, 217, 255, 307, 363, 381, 399, 403, 465, 511, 549, 553, 741, 781, 819, 847, 855, 871, 921, 931, 961, 993, 1023, 1093, 1143, 1209, 1281, 1407, 1651, 1659, 1723, 1729, 1767, 1815, 1893, 1953
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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a(7) = 39 because sigma(18) = 1+2+3+6+9+18 = 39, an odd number.
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MATHEMATICA
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a = {}; Do[ s = DivisorSigma[ 1, n ]; If[ OddQ[ s ], a = Append[ a, s ] ], {n, 1, 3000} ]; Union[ a ]
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CROSSREFS
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Cf. A007369.
Sequence in context: A080565 A164344 A002254 this_sequence A151875 A117533 A065057
Adjacent sequences: A060654 A060655 A060656 this_sequence A060658 A060659 A060660
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 18 2001
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