A062789 a(n) = gcd(n, phi(n) * (phi(n) + 1)).

1, 2, 3, 2, 5, 6, 7, 4, 3, 10, 11, 4, 13, 14, 3, 8, 17, 6, 19, 4, 3, 22, 23, 24, 5, 26, 9, 4, 29, 6, 31, 16, 3, 34, 5, 12, 37, 38, 3, 8, 41, 6, 43, 4, 15, 46, 47, 16, 7, 10, 3, 4, 53, 18, 5, 8, 3, 58, 59, 4, 61, 62, 9, 32, 1, 6, 67, 4, 3, 10, 71, 24, 73, 74, 5, 4, 1, 6, 79, 16, 27, 82, 83, 12

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..2000

Mathematica

Table[GCD[n, EulerPhi[n]*(EulerPhi[n] + 1)], {n, 75}] (* Stefan Steinerberger, Apr 03 2006 *)
ep[n_]:=Module[{epn=EulerPhi[n]}, GCD[n, epn(epn+1)]]; Array[ep, 90] (* Harvey P. Dale, Jun 23 2011 *)

Prog

(PARI) for (n=1, 2000, p=eulerphi(n); write("b062789.txt", n, " ", gcd(n, p*(p + 1)))) \\ Harry J. Smith, Aug 11 2009
(Haskell)
a062789 n = gcd n (phi * (phi + 1)) where phi = a000010 n
-- Reinhard Zumkeller, Oct 07 2015

Crossrefs

Cf. A009195, A000010, A039649.

Sequence in context: A287620 A304491 A277803 * A066069 A019530 A355263

Adjacent sequences: A062786 A062787 A062788 * A062790 A062791 A062792

Keyword

easy,nice,nonn

Author

Reinhard Zumkeller, Jul 19 2001

Extensions

More terms from Stefan Steinerberger, Apr 03 2006

More terms from Harry J. Smith, Aug 11 2009

Status

approved