A161661 a(1)=1. a(n) = smallest multiple of {number of divisors of a(n-1)} that is >= n.

1, 2, 4, 6, 8, 8, 8, 8, 12, 12, 12, 12, 18, 18, 18, 18, 18, 18, 24, 24, 24, 24, 24, 24, 32, 30, 32, 30, 32, 30, 32, 36, 36, 36, 36, 36, 45, 42, 40, 40, 48, 50, 48, 50, 48, 50, 48, 50, 54, 56, 56, 56, 56, 56, 56, 56, 64, 63, 60, 60, 72, 72, 72

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Mathematica

t = {1}; Do[d = DivisorSigma[0, t[[-1]]]; AppendTo[t, d*Ceiling[n/d]], {n, 2, 100}]; t (* T. D. Noe, Mar 23 2011 *)
nxt[{n_, a_}]:=Module[{d=DivisorSigma[0, a]}, {n+1, d*Ceiling[(n+1)/d]}]; Transpose[ NestList[nxt, {1, 1}, 70]][[2]] (* Harvey P. Dale, Oct 14 2015 *)

Crossrefs

Cf. A161660.

Sequence in context: A077988 A166880 A079088 * A115158 A107634 A060659

Adjacent sequences: A161658 A161659 A161660 * A161662 A161663 A161664

Keyword

nonn

Author

Leroy Quet, Jun 15 2009

Extensions

More terms from Sean A. Irvine, Mar 23 2011

Status

approved