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A144907 a(n) = 1 if n is prime, 2 * rad(n) if four divides n and rad(n) otherwise.

%I A144907 #11 Jan 03 2016 15:08:50
%S A144907 1,1,1,4,1,6,1,4,3,10,1,12,1,14,15,4,1,6,1,20,21,22,1,12,5,26,3,28,1,
%T A144907 30,1,4,33,34,35,12,1,38,39,20,1,42,1,44,15,46,1,12,7,10,51,52,1,6,55,
%U A144907 28,57,58,1,60,1,62,21,4,65,66,1,68,69,70,1,12,1,74,15,76,77,78,1,20,3,82
%N A144907 a(n) = 1 if n is prime, 2 * rad(n) if four divides n and rad(n) otherwise.
%H A144907 Reikku Kulon, <a href="/A144907/b144907.txt">Table of n, a(n) for n = 1..10000</a>
%t A144907 rad[n_]:= Module[{aux = FactorInteger[n]},Product[aux[[i, 1]],{i, Length[aux]}]]; a[n_] := Which[PrimeQ[n], 1, IntegerQ[n/4], 2*rad[n], True, rad[n]] Table[a[n], {n, 1, 100}] (* _José María Grau Ribas_, Feb 16 2010 *)
%o A144907 (Haskell)
%o A144907 a144907 x | a010051 x == 1 = 1
%o A144907           | x `mod` 4 == 0 = 2 * rad
%o A144907           | otherwise      = rad  where rad = a007947 x
%o A144907 -- _Reinhard Zumkeller_, Mar 12 2014
%Y A144907 Cf. A000040, A007947, A144100, A144310.
%K A144907 easy,nonn
%O A144907 1,4
%A A144907 _Reikku Kulon_, Sep 24 2008