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

1,1

Links

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

Formula

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

Example

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

Prog

(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

Crossrefs

A000010, A058515.

Sequence in context: A234749 A024546 A073542 * A353439 A117061 A341799

Adjacent sequences: A063441 A063442 A063443 * A063445 A063446 A063447

Keyword

nonn

Author

Labos Elemer, Jul 24 2001

Status

approved