A133582 a(n) is found from a(n-1) by dividing by D-1 and multiplying by D, where D is the smallest number that is not a divisor of a(n-1).

1, 2, 3, 6, 8, 12, 15, 30, 40, 60, 70, 105, 210, 280, 420, 480, 560, 840, 945, 1890, 2520, 2772, 3465, 6930, 9240, 10395, 20790, 27720, 30030, 40040, 60060, 68640, 80080, 120120, 135135, 270270, 360360, 384384, 480480, 540540, 617760, 720720, 765765

Offset

1,2

Links

Table of n, a(n) for n=1..43.

Example

Smallest number not a factor of 30 is 4, so next term after 30 is (30/3)*4 = 40.

Maple

A133582 := proc(n) option remember ; local d ; if n = 1 then 1; else for d from 2 do if A133582(n-1) mod d <> 0 then RETURN( A133582(n-1)*d/(d-1) ) ; fi ; od; fi ; end: seq(A133582(n), n=1..40) ; # R. J. Mathar, Jan 07 2008

Mathematica

a = {1, 2}; Do[i = 1; While[IntegerQ[a[[ -1]]/i], i++ ]; AppendTo[a, (i/(i - 1))*a[[ -1]]], {50}]; a (* Stefan Steinerberger, Dec 29 2007 *)
nxt[n_]:=Module[{d=First[Complement[Range[n], Divisors[n]]]}, d/(d-1)*n]; Join[{1, 2}, NestList[nxt, 3, 50]] (* Harvey P. Dale, Jul 10 2012 *)

Crossrefs

Sequence in context: A361922 A111242 A343820 * A325342 A085642 A270738

Adjacent sequences: A133579 A133580 A133581 * A133583 A133584 A133585

Keyword

nonn

Author

J. Lowell, Dec 26 2007

Extensions

More terms from Stefan Steinerberger, Dec 29 2007

Status

approved