

A070999


Numbers n such that the denominator of sum(k=1,n,1/gcd(n,k)) is not equal to n.


0



6, 15, 18, 21, 30, 33, 35, 42, 44, 45, 48, 51, 54, 60, 66, 69, 70, 78, 84, 87, 90, 99, 102, 105, 114, 119, 120, 123, 126, 132, 133, 135, 138, 140, 141, 144, 147, 150, 153, 159, 162, 165, 168, 174, 177, 180, 186, 195, 198, 204, 207, 210, 213, 217, 220, 221, 222
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Does lim n > infinity a(n)/n = 3 ?


LINKS

Table of n, a(n) for n=1..57.


EXAMPLE

sum(k=1,6,1/gcd(6,k))=7/2 hence 6 is in the sequence but sum(k=1,12,1/gcd(12,k))=77/12 so 12 is not in the sequence.


PROG

(PARI) for(n=1, 300, if(denominator(sum(i=1, n, 1/gcd(n, i)))<n, print1(n, ", ")))


CROSSREFS

Sequence in context: A274549 A099535 A302296 * A128693 A105285 A138922
Adjacent sequences: A070996 A070997 A070998 * A071000 A071001 A071002


KEYWORD

easy,nonn


AUTHOR

Benoit Cloitre, May 18 2002


STATUS

approved



