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Search: id:A006049
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| A006049 |
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Numbers n such that n and n+1 have same number of distinct prime divisors. |
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+0
2
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| 2, 3, 4, 7, 8, 14, 16, 20, 21, 31, 33, 34, 35, 38, 39, 44, 45, 50, 51, 54, 55, 56, 57, 62, 68, 74, 75, 76, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 111, 115, 116, 117, 118, 122, 123, 127, 133, 134, 135, 141, 142, 143, 144, 145, 146, 147, 152, 158, 159, 160, 161, 171, 175
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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C. Clawson, Mathematical mysteries, Plenum Press 1996, p. 250.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..2500
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MATHEMATICA
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f[n_] := Length@FactorInteger[n]; t = f /@ Range[175]; Flatten@Position[Rest[t] - Most[t], 0] (*Chandler*)
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CROSSREFS
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Cf. A001221, A052215, A107800.
Sequence in context: A051213 A066847 A057887 this_sequence A084541 A113050 A097110
Adjacent sequences: A006046 A006047 A006048 this_sequence A006050 A006051 A006052
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 27 2007
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