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A162361
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Central prime factor of A014612(n).
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6
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2, 2, 3, 2, 3, 2, 3, 3, 2, 3, 5, 2, 3, 3, 2, 5, 5, 2, 3, 2, 7, 3, 3, 5, 5, 3, 2, 3, 2, 5, 5, 3, 7, 2, 3, 7, 2, 5, 5, 3, 2, 3, 5, 7, 3, 2, 5, 5, 3, 2, 3, 5, 7, 2, 7, 11, 2, 7, 3, 5, 3, 3, 7, 2, 7, 5, 3, 3, 2, 5, 11, 5, 2, 5, 2, 3, 7, 5, 2, 3, 13, 7, 5, 3, 2, 7, 11, 3, 3, 5, 11, 7, 3, 2, 7, 3, 2, 7, 5, 2, 11, 3, 5
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(1)=2 since A014612(1) = 8 = 2*2*2.
a(2)=2 since A014612(2) = 12 = 2*2*3.
a(3)=3 since A014612(3) = 18 = 2*3*3.
a(4)=2 since A014612(4) = 20 = 2*2*5.
a(5)=3 since A014612(5) = 27 = 3*3*3.
a(6)=2 since A014612(6) = 28 = 2*2*7.
a(7)=3 since A014612(7) = 30 = 2*3*5.
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MAPLE
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A014612 := proc(n) option remember ; if n = 1 then 8 ; else for a from procname(n-1)+1 do if numtheory[bigomega](a) = 3 then RETURN(a) ; fi; od: fi; end:
A162361 := proc(n) tpr := A014612(n) ; pf := sort(convert(numtheory[factorset](tpr), list)) ; tpr/op(1, pf)/op(-1, pf) ; end:
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MATHEMATICA
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f[n_] := With[{fi = FactorInteger[n][[All, 1]]}, n/(fi[[1]] fi[[-1]])];
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PROG
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(PARI) isok(n) = bigomega(n)==3;
lista(nn) = {for (n=1, nn, if (isok(n), my(f=factor(n)[, 1]); print1(n/(vecmin(f)*vecmax(f)), ", ")); ); } \\ Michel Marcus, Feb 25 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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