A119989 a(1)=1. a(n) = number of terms among the first (n-1) terms of the sequence which are coprime to n(n+1)/2.

1, 1, 2, 2, 4, 5, 3, 3, 5, 7, 5, 6, 11, 6, 4, 9, 11, 12, 8, 4, 11, 18, 9, 6, 21, 15, 8, 13, 14, 15, 17, 8, 16, 24, 7, 12, 36, 21, 8, 15, 20, 21, 19, 7, 22, 45, 14, 11, 32, 25, 14, 26, 33, 23, 10, 13, 35, 57, 14, 14, 60, 30, 15, 21, 24, 34, 33, 17, 25, 42, 21, 21, 72, 34, 14, 21, 26, 41

Offset

1,3

Links

Table of n, a(n) for n=1..78.

Prog

(PARI) lista(nn)={my(v=[1]); for(n=2, nn, a=0; q=n*(n+1)/2; for(j=1, n-1, if(gcd(v[j], q)==1, a++)); v=concat(v, a)); v} \\ Klaus Brockhaus, Aug 15 2006

Crossrefs

Cf. A123953.

Sequence in context: A211188 A057899 A210200 * A137605 A375570 A328728

Adjacent sequences: A119986 A119987 A119988 * A119990 A119991 A119992

Keyword

nonn,changed

Author

Leroy Quet, Aug 03 2006

Extensions

More terms from Klaus Brockhaus, Aug 15 2006

Status

approved