A127418 a(1)=1; for n>1, a(n) = the number of earlier terms a(k), 1<k<=n-1, such that (a(k)+n) is coprime to k.

1, 1, 1, 3, 1, 5, 3, 6, 4, 7, 3, 10, 8, 8, 10, 11, 7, 11, 10, 13, 13, 14, 10, 18, 15, 16, 16, 17, 13, 20, 20, 16, 23, 21, 17, 25, 24, 21, 23, 25, 19, 30, 25, 25, 25, 29, 23, 36, 29, 29, 32, 33, 26, 41, 28, 37, 32, 37, 30, 41, 32, 41, 33, 42, 32, 51, 36, 44, 39, 43, 38, 52, 41, 44

Offset

1,4

Comments

The value of a(1) = 1 is arbitrary. a(1) can be any integer and the rest of the sequence would remain unchanged.

Links

Table of n, a(n) for n=1..74.

Example

a(1)+11 = 12 is coprime to 1; a(5)+11 = 12 is coprime to 5; and a(8)+11 = 17 is coprime to 8. These 3 are the only cases where (a(k)+11) is coprime to k, for 1 <=k <=10. So a(11) = 3.

Mathematica

f[l_List] := Block[{n = Length[l] + 1}, Append[l, Count[Table[GCD[l[[k]] + n, k], {k, n - 1}], 1]]]; Nest[f, {1}, 74] (* Ray Chandler, Jan 22 2007 *)

Crossrefs

Cf. A127417.

Sequence in context: A109606 A318727 A307806 * A099550 A349341 A099549

Adjacent sequences: A127415 A127416 A127417 * A127419 A127420 A127421

Keyword

nonn

Author

Leroy Quet, Jan 13 2007

Extensions

Extended by Ray Chandler, Jan 22 2007

Status

approved