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A099985
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a(n) = rad(2n), where rad = A007947.
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5
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2, 2, 6, 2, 10, 6, 14, 2, 6, 10, 22, 6, 26, 14, 30, 2, 34, 6, 38, 10, 42, 22, 46, 6, 10, 26, 6, 14, 58, 30, 62, 2, 66, 34, 70, 6, 74, 38, 78, 10, 82, 42, 86, 22, 30, 46, 94, 6, 14, 10, 102, 26, 106, 6, 110, 14, 114, 58, 118, 30, 122, 62, 42, 2, 130, 66, 134, 34, 138, 70, 142, 6
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Sum_{k=1..n} a(k) ~ c * n^2, where c = (4/5) * Product_{p prime} (1 - 1/(p*(p+1))) = (4/5) * A065463 = 0.563553... . - Amiram Eldar, Nov 19 2022
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MAPLE
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with(numtheory): A007947 := proc(n) local i, t1, t2; t1 :=ifactors(n)[2]; t2 := mul(t1[i][1], i=1..nops(t1)); end: seq(A007947(2*n), n=1..78); # Emeric Deutsch, Dec 15 2004
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MATHEMATICA
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Table[Product[p, {p, Select[Divisors[2 n], PrimeQ]}], {n, 100}] (* Wesley Ivan Hurt, May 08 2022 *)
a[n_] := Times @@ (First /@ FactorInteger[2*n]); Array[a, 100] (* Amiram Eldar, Nov 19 2022 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,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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