A098709 a(n) = smallest positive multiple of (number of terms of {a(1), a(2), ..., a(n-1)} that are coprime to n) that is not among previous terms of sequence.

1, 2, 4, 3, 8, 5, 6, 9, 10, 12, 20, 14, 24, 16, 18, 28, 32, 22, 36, 15, 30, 25, 44, 21, 54, 7, 45, 35, 56, 26, 60, 40, 17, 50, 72, 42, 108, 11, 63, 48, 80, 55, 84, 96, 75, 90, 46, 64, 39, 27, 100, 112, 52, 88, 34, 13, 128, 126, 58, 65, 120, 19, 150, 140, 160, 81, 66, 180, 37

Offset

1,2

Comments

This sequence does not include all positive integers; the first few omitted values are 73, 163, 177, 197, 229. At n = 931, the number of noncomposite values in the sequence exceeds 77 and numbers in this range can be divisible by at most 4 distinct primes, so any value from that point on must exceed 73. (This is not quite a proof; there could stop being any prime values in the sequence until p_k primorial catches up with the difference, but it is obvious that this does not happen.) - Franklin T. Adams-Watters, Jun 02 2006

Links

Table of n, a(n) for n=1..69.

Example

a(8) is 9 because there are 3 terms of the sequence among the first 7 terms which are coprime to 8 and 9 is the smallest positive multiple of 3 not among the first 7 terms of the sequence.

Crossrefs

Sequence in context: A305427 A269375 A135141 * A054238 A225589 A245603

Adjacent sequences: A098706 A098707 A098708 * A098710 A098711 A098712

Keyword

nonn

Author

Leroy Quet, Sep 28 2004

Extensions

More terms from Franklin T. Adams-Watters, Jun 02 2006

Status

approved