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A085080
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Smallest k such that n, k and n+k have the same prime signature (canonical form), or 0 if no such number exists.
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0
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0, 3, 2, 0, 2, 15, 0, 0, 0, 55, 2, 63, 0, 21, 6, 0, 2, 45, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 1. a(n) = 0 if n is a perfect prime power or a prime such that n+2 is composite. The zero entries in other cases suggest a generalization of Fermat's last theorem. a(n) = 2 if n and n+2 form a twin prime pair.
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EXAMPLE
| a(12) = 63 as 12 + 63 = 75, 2^2*3 + 3^2*7 = 5^2*3, all have the prime signature p^2*q.
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CROSSREFS
| Sequence in context: A077814 A131728 A075115 * A079714 A190710 A114907
Adjacent sequences: A085077 A085078 A085079 * A085081 A085082 A085083
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KEYWORD
| more,nonn
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AUTHOR
| Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), Jul 01 2003
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