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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. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 1 04:58 EDT 2020. Contains 333155 sequences. (Running on oeis4.)