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A121494
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Composite numbers n such that tau(n) = tau(2n+1).
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0
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4, 10, 27, 34, 38, 46, 55, 57, 62, 76, 77, 91, 93, 106, 118, 123, 129, 133, 136, 143, 145, 159, 161, 177, 185, 201, 203, 205, 206, 212, 213, 218, 226, 232, 235, 259, 267, 291, 295, 297, 298, 305, 310, 314, 322, 327, 334, 335, 339, 343, 357, 358, 365, 370, 377
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| Composite terms of A074821, while prime terms of A074821 are Sophie Germain primes A005384.
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EXAMPLE
| 10 is OK since both 10 and 2*10+1=21 have 4 divisors;
{1,2,5,10} and {1,3,7,21}.
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CROSSREFS
| Cf. A005384, A074821.
Sequence in context: A130583 A105999 A192210 * A122744 A192879 A077923
Adjacent sequences: A121491 A121492 A121493 * A121495 A121496 A121497
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KEYWORD
| nonn
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Aug 03 2006
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