A087623 Triangle read by rows: T(m,n) is the cardinality of the set {k in [1,n-1] : gcd(k,n)=m}.

0, 0, 1, 0, 0, 2, 0, 0, 0, 2, 0, 0, 0, 1, 4, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 2, 6, 0, 0, 0, 0, 0, 1, 0, 4, 0, 0, 0, 0, 0, 0, 0, 2, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 10, 0, 0, 0, 0, 0, 0

Offset

1,6

Comments

A generalization of Euler's phi function: T(1,n)=phi(n).

Links

Table of n, a(n) for n=1..72.

Example

T(2,4)=1 because gcd(1,4)=1, gcd(2,4)=2, gcd(3,4)=1.

Crossrefs

Cf. A000010.

Sequence in context: A083914 A083891 A363860 * A265260 A363888 A338268

Adjacent sequences: A087620 A087621 A087622 * A087624 A087625 A087626

Keyword

nonn,easy,tabl

Author

Michele Dondi (bik.mido(AT)tiscalinet.it), Sep 14 2003

Status

approved