A217619 a(n) = m/(12*n) where m is the least multiple of n that satisfies phi(m) = phi(m+6*n).

2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 5, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 5, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2

Offset

1,1

Comments

It appears that A217140(n) is divisible by 12 for all n.

Links

Table of n, a(n) for n=1..87.

S. W. Graham, J. J. Holt and C. Pomerance, On the solutions to phi(n) = phi(n+k), Number Theory in Progress, K. Gyory, H. Iwaniec, and J. Urbanowicz, eds., vol. 2, de Gruyter, Berlin and New York, 1999, pp. 867-882.

Formula

a(n) = A217140(n)/12.

Example

A179188(1)=24 is divisible by 1 and the quotient 24 when divided by 12 gives 2, so a(1)=2.
A217139(1)=48 is divisible by 2 and the quotient 24 when divided by 12 gives 2, so a(2)=2.
A217140(5)=36 and 36/12=3, so a(5)=3.

Crossrefs

Cf. A179188, A217139, A217141, A217068, A217140.

Sequence in context: A183024 A067131 A094915 * A187186 A259651 A253719

Adjacent sequences: A217616 A217617 A217618 * A217620 A217621 A217622

Keyword

nonn

Author

Jonathan Sondow and Michel Marcus, Oct 09 2012

Status

approved