A118809 a(1) = 1. a(n) = (number of earlier terms which divide n)th positive integer not occurring among the earlier terms of the sequence.

1, 2, 3, 5, 6, 9, 4, 10, 11, 13, 8, 16, 12, 14, 17, 20, 15, 22, 7, 25, 21, 24, 18, 31, 26, 28, 27, 33, 19, 36, 29, 35, 34, 37, 38, 44, 30, 40, 39, 47, 23, 48, 32, 49, 46, 45, 42, 57, 50, 54, 51, 55, 41, 61, 56, 63, 58, 59, 52, 70, 53, 62, 67, 68, 64, 72, 60, 73, 66, 77, 43, 83

Offset

1,2

Comments

Likely a permutation of the positive integers.

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Example

The first 7 terms of the sequence are 1,2,3,5,6,9,4. Of these there are 3 terms (1, 2 and 4) that divide 8, so we want for a(8) the 3rd positive integer not among the first 7 terms of the sequence (i.e., we want the third term of 7,8,10,11,...). So a(8)= 10.

Maple

A118809 := proc(nmin) local a, anxt, i, n, j ; a := [1] ; while nops(a) < nmin do n := nops(a)+1 ; i := 0 ; for j in a do if n mod j = 0 then i := i+1 ; fi ; od: anxt := 0 ; while i > 0 do anxt := anxt+1 ; while anxt in a do anxt := anxt+1 ; od ; i := i-1; od ; a := [op(a), anxt] ; od; a ; end: A118809(100) ; # R. J. Mathar, Sep 06 2007

Mathematica

Fold[Append[#1, Complement[Range[2 Max@#1], #1][[Length@Intersection[Divisors[#2], #1]]]] &, {1}, Range[2, 72]] (* Ivan Neretin, Feb 06 2018 *)

Crossrefs

Cf. A118810.

Sequence in context: A287876 A073673 A179217 * A121048 A075389 A053784

Adjacent sequences: A118806 A118807 A118808 * A118810 A118811 A118812

Keyword

nonn

Author

Leroy Quet, Apr 30 2006

Extensions

More terms from R. J. Mathar, Sep 06 2007

Status

approved