

A124201


a(n) = nth positive integer from among those positive integers which are coprime to every noncomposite (1 or prime) which is < n and does not divide n.


0



1, 2, 5, 5, 13, 7, 23, 17, 27, 17, 43, 18, 59, 32, 43, 43, 79, 36, 97, 50, 71, 62, 113, 58, 125, 79, 109, 79, 157, 53, 173, 118, 131, 113, 167, 94, 211, 134, 167, 125, 239, 96, 257, 158, 191, 173, 281, 146, 283, 167, 237, 194, 331, 167, 295, 202, 267, 227, 373, 144
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

For which n's are n and a(n) coprime?


LINKS



EXAMPLE

The primes < 8 and coprime to 8 are 3, 5 and 7. The positive integers which are coprime to these primes (i.e. which are coprime to 3*5*7) are 1, 2, 4, 8, 11, 13, 16, 17, 19, ...a(8) is the 8th of these integers, which is 17.


MATHEMATICA

f[n_] := Block[{c = n, k = 0, p}, p = Times @@ Select[Range[n  1], PrimeQ[ # ] && GCD[ #, n] == 1 &]; While[c > 0, k++; While[GCD[k, p] > 1, k++ ]; c; ]; k]; Table[f[n], {n, 61}] (* Ray Chandler, Dec 11 2006 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS



STATUS

approved



