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A045920
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Numbers n such that factorizations of n and n+1 have same number of primes (including multiplicities).
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9
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2, 9, 14, 21, 25, 27, 33, 34, 38, 44, 57, 75, 85, 86, 93, 94, 98, 116, 118, 121, 122, 124, 133, 135, 141, 142, 145, 147, 153, 158, 164, 170, 171, 174, 177, 201, 202, 205, 213, 214, 217, 218, 230, 244, 245, 253, 284, 285, 296, 298, 301, 302, 326, 332, 334, 350, 356, 361
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A115186 is a subsequence: A001222(A115186(n))=A001222(A115186(n)+1)=n. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 16 2006
Indices k such that A076191(k) = 0. [From Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 10 2008]
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REFERENCES
| C. Clawson, Mathematical mysteries, Plenum Press 1996, p. 250
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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MATHEMATICA
| f[n_]:=Plus@@Last/@FactorInteger[n]; lst={}; Do[If[f[n]==f[n+1], AppendTo[lst, n]], {n, 0, 6!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), May 12 2010]
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PROG
| (Haskell)
import Data.List (elemIndices)
a045920 n = a045920_list !! (n-1)
a045920_list = map (+ 1) $ elemIndices 0 $
zipWith (-) (tail a001222_list) a001222_list
-- Reinhard Zumkeller, Oct 11 2011
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CROSSREFS
| Sequence in context: A144472 A071343 A043401 * A071344 A106360 A024470
Adjacent sequences: A045917 A045918 A045919 * A045921 A045922 A045923
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KEYWORD
| nice,nonn
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AUTHOR
| Felice Russo (frusso(AT)micron.com)
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EXTENSIONS
| More terms from David W. Wilson (davidwwilson(AT)comcast.net)
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