A001598 Number of terms in {b(1)..b(n)} relatively prime to b(n), where b(n) = A001597(n).

1, 1, 1, 3, 2, 5, 5, 4, 2, 9, 5, 8, 5, 13, 12, 8, 5, 17, 8, 6, 11, 14, 11, 23, 7, 23, 26, 11, 16, 14, 15, 31, 10, 28, 16, 24, 15, 37, 9, 39, 16, 20, 27, 20, 31, 14, 43, 47, 23, 32, 20, 51, 17, 14, 54, 24, 30, 28, 27, 40, 57, 61, 20, 56, 26, 42, 30, 28, 68, 22

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

References

• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• H. W. Gould, Problem H-170, Fib. Quart., 8 (1970), p. 268.

Programs

Mathematica

nn = 10^4; t = Join[{1}, Union[Flatten[Table[n^i, {i, Prime[Range[PrimePi[Log[2, nn]]]]}, {n, 2, nn^(1/i)}]]]]; Table[Count[GCD[Take[t, n], t[[n]]], 1], {n, Length[t]}] (* T. D. Noe, Aug 09 2012 *)

Extensions

a(1) added by T. D. Noe, Aug 09 2012