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A099985 a(n) = rad(2n), where rad = A007947.

%I A099985 #24 Nov 19 2022 04:45:48
%S A099985 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,
%T A099985 14,58,30,62,2,66,34,70,6,74,38,78,10,82,42,86,22,30,46,94,6,14,10,
%U A099985 102,26,106,6,110,14,114,58,118,30,122,62,42,2,130,66,134,34,138,70,142,6
%N A099985 a(n) = rad(2n), where rad = A007947.
%C A099985 Bisection of A007947.
%H A099985 Antti Karttunen, <a href="/A099985/b099985.txt">Table of n, a(n) for n = 1..20000</a>
%F A099985 a(n) = 2 * A204455(n).
%F A099985 a(n) = A007947(2n). - _Wesley Ivan Hurt_, May 07 2022
%F A099985 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
%p A099985 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
%t A099985 Table[Product[p, {p, Select[Divisors[2 n], PrimeQ]}], {n, 100}] (* _Wesley Ivan Hurt_, May 08 2022 *)
%t A099985 a[n_] := Times @@ (First /@ FactorInteger[2*n]); Array[a, 100]  (* _Amiram Eldar_, Nov 19 2022 *)
%o A099985 (PARI) A099985(n) = factorback(factorint(n+n)[, 1]); \\ _Antti Karttunen_, May 08 2022
%Y A099985 Cf. A007947, A065463, A099984, A204455.
%K A099985 nonn,easy
%O A099985 1,1
%A A099985 _N. J. A. Sloane_, Nov 19 2004
%E A099985 More terms from _Emeric Deutsch_, Dec 15 2004
%E A099985 Name changed by _Wesley Ivan Hurt_, May 07 2022