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A078613
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Same numbers of distinct prime factors of forms 4*k+1 and 4*k+3.
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0
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1, 2, 4, 8, 15, 16, 30, 32, 35, 39, 45, 51, 55, 60, 64, 70, 75, 78, 87, 90, 91, 95, 102, 110, 111, 115, 117, 119, 120, 123, 128, 135, 140, 143, 150, 153, 155, 156, 159, 174, 175, 180, 182, 183, 187, 190, 203, 204, 215, 219, 220, 222, 225, 230, 234, 235, 238, 240
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Equivalently, numbers n such that A005089(n) = A005091(n).
A001221(a(n)) and a(n) are of opposite parity.
If m is in the sequence, then also 2*m.
Conjecture : a(n) is asymptotic to c*n where c is around 4 - Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 06 2003
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EXAMPLE
| n = 99 = [(4*0+3)^2]*[(4*1+1)], therefore 99 is a term.
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MATHEMATICA
| fQ[n_]:=Plus@@((Mod[#[[1]], 4]-2)&/@If[n==1, {}, FactorInteger[n]])==0; Select[Range[240], fQ] (* Ray Chandler, Dec 18 2011*)
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CROSSREFS
| Cf. A072202.
Sequence in context: A019278 A084345 A084561 * A072202 A076351 A140117
Adjacent sequences: A078610 A078611 A078612 * A078614 A078615 A078616
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KEYWORD
| nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Dec 10 2002
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EXTENSIONS
| Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 18 2011
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