A063444 Smallest number such that GCD of EulerPhi of 2 consecutive integer equals 2n.

3, 12, 13, 15, 121, 35, 86, 64, 37, 99, 726, 72, 158, 196, 61, 96, 4931, 73, 7639, 175, 343, 267, 2302, 104, 250, 676, 162, 637, 3481, 154, 21142, 192, 2178, 411, 5041, 814, 446, 1145, 157, 164, 6971, 1348, 14878, 1334, 542, 2115, 22090, 193, 2842, 2200

Offset: 1

Author

Labos Elemer, Jul 24 2001

Keywords

• nonn

Examples

			n = 10, a(10) = 99, Phi(99) = 60, Phi(100) = 40, GCD[60,40] = 2n = 20.
		

Links

• Harry J. Smith, Table of n, a(n) for n=1,...,350

Crossrefs

A000010, A058515.

Programs

PARI

{ for (n=1, 350, x=1; while (gcd(eulerphi(x+1), eulerphi(x)) != 2*n, x++); write("b063444.txt", n, " ", x) ) } \\ Harry J. Smith, Aug 21 2009

Formula

Min{x; GCD[Phi[x+1], Phi[x]]=2n}=Min{x; A058515[x]=2n}