A114652 a(1)=1. For n>1, a(n) = a(n-1) + (number of terms among {a(1),a(2),...,a(n-1)} which are coprime to n).

1, 2, 4, 5, 8, 10, 16, 18, 25, 26, 36, 39, 49, 53, 61, 68, 83, 90, 108, 114, 127, 136, 158, 166, 186, 194, 213, 222, 250, 256, 285, 296, 318, 329, 355, 365, 399, 412, 437, 448, 488, 498, 540, 556, 580, 595, 640, 653, 696, 708, 739, 757, 807, 823, 865, 884, 922

Offset

1,2

Links

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

Example

Among the first 5 terms of the sequence (1,2,4,5,8) there are 2 terms (1, 5) which are coprime to 6. So a(6) = a(5) + 2 = 10.

Mathematica

f[l_] := Append[l, Last[l] + Length[Select[l, GCD[ #, Length[l] + 1] == 1 &]]]; Nest[f, {1}, 56] (* Ray Chandler, Dec 23 2005 *)
a[1] = 1; a[n_] := a[n] = a[n - 1] + Count[GCD[Array[a, n - 1], n], 1]; Array[a, 57] (* Robert G. Wilson v *)

Crossrefs

Cf. A114653.

Sequence in context: A180252 A191203 A216686 * A191288 A181666 A067943

Adjacent sequences: A114649 A114650 A114651 * A114653 A114654 A114655

Keyword

nonn

Author

Leroy Quet, Dec 21 2005

Extensions

Extended by Ray Chandler and Robert G. Wilson v, Dec 23 2005

Status

approved