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

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, 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, 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

Offset: 1

Author

Reikku Kulon, Sep 24 2008

Keywords

• easy
• nonn

Links

• Reikku Kulon, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A007947, A144100, A144310.

Programs

Haskell

a144907 x | a010051 x == 1 = 1
          | x `mod` 4 == 0 = 2 * rad
          | otherwise      = rad  where rad = a007947 x
-- Reinhard Zumkeller, Mar 12 2014

Mathematica

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 *)