A070547 - OEIS

A070547

a(n)=Card( k, 0<k<n such that phi(k) divides phi(n-k)).

0, 1, 2, 2, 2, 3, 4, 4, 5, 6, 5, 5, 7, 6, 7, 8, 7, 9, 5, 10, 9, 10, 9, 7, 11, 9, 10, 10, 8, 9, 10, 11, 13, 12, 12, 13, 11, 11, 12, 14, 12, 13, 8, 16, 15, 16, 15, 11, 19, 16, 12, 15, 11, 16, 15, 17, 16, 15, 10, 14, 15, 12, 20, 15, 20, 18, 11, 17, 16, 18, 16, 18, 15, 18, 18, 16, 18

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..77.

PROG

(PARI) for(n=1, 100, print1(sum(i=1, n-1, if(eulerphi(n-i)%eulerphi(i), 0, 1)), ", "))

CROSSREFS

Sequence in context: A303003 A063124 A358901 * A319922 A289139 A094838

Adjacent sequences: A070544 A070545 A070546 * A070548 A070549 A070550

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, May 02 2002

STATUS

approved