A188525 a(n) = rad(rad(n)^2+1), where rad = A007947.

2, 5, 10, 5, 26, 37, 10, 5, 10, 101, 122, 37, 170, 197, 226, 5, 290, 37, 362, 101, 442, 485, 530, 37, 26, 677, 10, 197, 842, 901, 962, 5, 1090, 1157, 1226, 37, 1370, 85, 1522, 101, 58, 1765, 370, 485, 226, 2117, 2210, 37, 10, 101, 2602, 677, 2810, 37

Offset: 1

Author

Jonathan Vos Post, Apr 03 2011

Keywords

• nonn
• easy

Examples

			a(7) = rad(rad(7)^2 + 1) = rad(7^2 + 1) = rad(50) = 10.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007947, A078322.

Programs

Magma

[ &*PrimeDivisors((&*PrimeDivisors(n))^2+1): n in [1..51] ]; // Bruno Berselli, Apr 04 2011

Maple

with(numtheory):
rad:= n-> mul(i, i=factorset(n)):
a:= n-> rad(rad(n)^2+1):
seq(a(n), n=1..70);  # Alois P. Heinz, Apr 03 2011

Mathematica

rad[n_] := Times @@ FactorInteger[n][[All, 1]];
a[n_] := rad[rad[n]^2 + 1];
Array[a, 70] (* Jean-François Alcover, Mar 27 2017 *)

PARI

rad(n)=my(f=factor(n)[,1]);prod(i=1,#f,f[i])
a(n)=rad(rad(n)^2+1) \\ Charles R Greathouse IV, Aug 08 2013

Formula

a(n) = A007947(A078615(n)+1). - R. J. Mathar, Apr 04 2011