A127462 a(1)=1; for n>1, a(n) = number of earlier terms a(k), 1<=k<=n-1, such that (k+a(k)) is coprime to n.

1, 0, 2, 1, 2, 3, 5, 4, 5, 2, 10, 3, 12, 5, 5, 8, 16, 5, 17, 6, 9, 9, 21, 7, 18, 13, 15, 12, 28, 6, 28, 16, 16, 17, 22, 11, 36, 18, 20, 18, 40, 12, 41, 22, 18, 23, 45, 14, 40, 22, 26, 26, 52, 16, 41, 22, 27, 28, 56, 13, 60, 29, 26, 33, 49, 20, 66, 34, 34, 23, 70, 24, 70, 39, 33, 36, 56

Offset

1,3

Links

Table of n, a(n) for n=1..77.

Example

(a(3)+3) is coprime to 6; (a(4)+4) is coprime to 6; and (a(5)+5) is coprime to 6. These 3 cases are the only cases where (a(k)+k) is coprime to 6, for 1<=k<=5. So a(6)=3.

Mathematica

f[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[Table[GCD[n, k + l[[k]]], {k, n - 1}], 1]]]; Nest[f, {1}, 76] (* Ray Chandler, Jan 22 2007 *)

Crossrefs

Cf. A127460, A127463.

Sequence in context: A259439 A274491 A076492 * A106436 A363226 A075758

Adjacent sequences: A127459 A127460 A127461 * A127463 A127464 A127465

Keyword

nonn

Author

Leroy Quet, Jan 15 2007

Extensions

Extended by Ray Chandler, Jan 22 2007

Status

approved