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A100368
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Even numbers of which number of distinct prime-factors equals 2 and the odd factor is prime.
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4
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6, 10, 12, 14, 20, 22, 24, 26, 28, 34, 38, 40, 44, 46, 48, 52, 56, 58, 62, 68, 74, 76, 80, 82, 86, 88, 92, 94, 96, 104, 106, 112, 116, 118, 122, 124, 134, 136, 142, 146, 148, 152, 158, 160, 164, 166, 172, 176, 178, 184, 188, 192, 194, 202, 206, 208, 212, 214, 218, 224
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| A proper subset of A098202. E.g. 210 is not here, but it is there. Also differs from A100367: 36,100,108,196 etc.. are missing here. Different also from A036348 because 90,180 are not here.
A128691 is a subsequence; A078834(a(n)) = A006530(a(n)). [Reinhard Zumkeller, Sep 19 2011]
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
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FORMULA
| Numbers of the form 2^k*p where k>0, p is an odd prime.
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MATHEMATICA
| <<NumberTheory`NumberTheoryFunctions` p2[x_] :=Part[PrimeFactorList[x], 2]; lf[x_] :=Length[FactorInteger[x]]; ta={{0}}; Do[If[Equal[lf[n], 2]&&EvenQ[n]&&IntegerQ[Log[2, n/p2[n]]], ta=Append[ta, n]; Print[n]], {n, 1, 256}]; ta=Delete[ta, 1]
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PROG
| (Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a100368 n = a100368_list !! (n-1)
a100368_list = f (singleton 6) (tail a065091_list) where
f s ps'@(p:ps) | mod m 4 > 0 = m : f (insert (2*p) $ insert (2*m) s') ps
| otherwise = m : f (insert (2*m) s') ps'
where (m, s') = deleteFindMin s
-- Reinhard Zumkeller, Sep 19 2011
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CROSSREFS
| Cf. A001221, A098902, A100367, A036348.
Cf. A100484.
Sequence in context: A088829 A036348 * A128691 A028919 A134620 A108315
Adjacent sequences: A100365 A100366 A100367 * A100369 A100370 A100371
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Nov 22 2004
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