A130420 a(n) = n-th positive integer which is coprime to n!!, where n!! = n*(n-2)*(n-4)..*(2 or 1).

1, 3, 4, 7, 8, 17, 16, 23, 19, 37, 29, 43, 37, 59, 41, 67, 53, 73, 62, 83, 67, 101, 79, 107, 83, 127, 89, 137, 103, 149, 113, 157, 122, 173, 128, 181, 139, 197, 146, 211, 158, 227, 173, 233, 179, 251, 194, 263, 199, 271, 206, 281, 223, 293, 227, 311, 233, 331, 251

Offset

1,2

Links

Table of n, a(n) for n=1..59.

Example

3!! = 3; the first number coprime to 3 is 1, the second one is 2, the third one is 4. Thus a(3) = 4.

Mathematica

a[n_] := Module[{in}, in = 0; k = 0; While[in != n, k++; If[GCD[n!!, k] == 1, in++ ]]; k]; Table[a[i], {i, 1, 80}] (* Stefan Steinerberger, May 30 2007 *)

Crossrefs

Cf. A130419, A119992.

Sequence in context: A117587 A359747 A244930 * A214096 A169943 A215110

Adjacent sequences: A130417 A130418 A130419 * A130421 A130422 A130423

Keyword

less,nonn

Author

Leroy Quet, May 25 2007

Extensions

More terms from Stefan Steinerberger, May 30 2007

Status

approved