A126327 a(1) = 1. a(n) = smallest positive multiple of (number of earlier terms in sequence which divide n) which has yet to appear in the sequence.

1, 2, 3, 4, 5, 6, 7, 9, 12, 15, 8, 18, 10, 21, 16, 20, 11, 24, 13, 30, 28, 27, 14, 32, 22, 33, 36, 42, 17, 40, 19, 48, 44, 39, 45, 54, 23, 51, 52, 56, 25, 64, 26, 60, 66, 57, 29, 50, 34, 72, 68, 78, 31, 80, 63, 88, 76, 69, 35, 84, 37, 75, 90, 49, 81, 96, 38, 102, 92, 70, 41, 108

Offset

1,2

Links

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

Example

There are three terms among the first 8 terms of the sequence which divide 9 (a(1)=1,a(3)=3,a(8)=9). So a(9) is the smallest multiple of 3 which does not occur among the first 8 terms of the sequence. 3,6 and 9 occur earlier in the sequence, so a(9) = 12.

Mathematica

a = {1}; Do[AppendTo[a, Min[Complement[Range[Max[a] + 1]*Count[a, x_ /; Divisible[n, x]], a]]], {n, 2, 72}]; a (* Ivan Neretin, Sep 03 2015 *)

Prog

(PARI) S=Set([1]); for(n=2, 100, d=length(setintersect(S, Set(divisors(n)))); k=d; while(setsearch(S, k), k+=d); S=setunion(S, [k]); print1(k, ", "); ) \\ Max Alekseyev, Jun 02 2007

Crossrefs

Sequence in context: A371248 A059759 A042952 * A328116 A193286 A098132

Adjacent sequences: A126324 A126325 A126326 * A126328 A126329 A126330

Keyword

nonn,look

Author

Leroy Quet, Mar 09 2007

Extensions

More terms from Max Alekseyev, Jun 02 2007

Status

approved