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A144907 a(n) = 1 if n is prime, 2 * rad(n) if four divides n and rad(n) otherwise. 3

%I

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

%H Reikku Kulon, <a href="/A144907/b144907.txt">Table of n, a(n) for n = 1..10000</a>

%t 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 (Haskell)

%o a144907 x | a010051 x == 1 = 1

%o | x `mod` 4 == 0 = 2 * rad

%o | otherwise = rad where rad = a007947 x

%o -- _Reinhard Zumkeller_, Mar 12 2014

%Y Cf. A000040, A007947, A144100, A144310.

%K easy,nonn

%O 1,4

%A _Reikku Kulon_, Sep 24 2008

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Last modified April 18 10:21 EDT 2021. Contains 343087 sequences. (Running on oeis4.)