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A170825
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a(n) is the product of the distinct primes of form 6*k-1 that divide n.
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4
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1, 1, 1, 1, 5, 1, 1, 1, 1, 5, 11, 1, 1, 1, 5, 1, 17, 1, 1, 5, 1, 11, 23, 1, 5, 1, 1, 1, 29, 5, 1, 1, 11, 17, 5, 1, 1, 1, 1, 5, 41, 1, 1, 11, 5, 23, 47, 1, 1, 5, 17, 1, 53, 1, 55, 1, 1, 29, 59, 5, 1, 1, 1, 1, 5, 11, 1, 17, 23, 5, 71, 1, 1, 1, 5, 1, 11, 1, 1, 5, 1, 41, 83, 1, 85, 1, 29, 11, 89, 5, 1
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OFFSET
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1,5
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LINKS
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FORMULA
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MAPLE
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A170825 := proc(n) a := 1 ; for p in numtheory[factorset](n) do if p mod 6 = 5 then a := a*p ; end if ; end do ; a ; end proc: seq(A170825(n), n=1..120) ; # R. J. Mathar, Jan 21 2010
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MATHEMATICA
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Table[Times@@Select[Transpose[FactorInteger[n]][[1]], IntegerQ[(#+1)/6]&], {n, 100}] (* Harvey P. Dale, Nov 01 2013 *)
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PROG
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(PARI) a(n) = my(f=factor(n)); for(i=1, #f~, f[i, 2] = (f[i, 1]%6)==5); factorback(f); \\ Michel Marcus, Sep 30 2020
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CROSSREFS
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KEYWORD
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nonn,mult,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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