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A140999 Members of A067128 that are the smallest numbers with their prime signatures. 4
1, 2, 4, 6, 8, 12, 24, 30, 36, 48, 60, 72, 96, 120, 180, 240, 360, 420, 480, 720, 840, 1080, 1260, 1440, 1680, 2160, 2520, 3360, 4320, 4620, 5040, 7560, 9240, 10080, 12600, 13860, 15120, 18480, 20160, 25200, 27720, 30240, 36960, 37800, 40320, 45360 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Includes all members of A002182.

Conjecture (false!): includes all members of A094348.

Contribution from Matthew Vandermast, Oct 10 2008: (Start)

Counterexample to conjecture: 5354228880, the smallest positive multiple of the first 23 positive integers, does not belong to A067128. It is the smallest member of A003418 (a subsequence of A094348) not to be largely composite.

Intersection of A067128 and A025487.

Includes all members of A097212. (End)

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1000

EXAMPLE

3 doesn't qualify because it's not the smallest number with its prime signature. 16 does not qualify because it's not a member of A067128.

MATHEMATICA

PrimeExponents[n_] := Last /@ FactorInteger[n]; lpe = {}; ln = {1}; dm=1; Do[d=DivisorSigma[0, n]; If[d>=dm, dm=d; pe = Sort@PrimeExponents@n; If[ FreeQ[lpe, pe], AppendTo[lpe, pe]; AppendTo[ln, n]]], {n, 2, 50000}]; ln (* Amiram Eldar, Jun 20 2019 after Robert G. Wilson v at A025487 *)

CROSSREFS

Sequence in context: A118563 A228515 A164145 * A168267 A308912 A301414

Adjacent sequences:  A140996 A140997 A140998 * A141000 A141001 A141002

KEYWORD

nonn

AUTHOR

J. Lowell, Jul 28 2008

EXTENSIONS

More terms from Matthew Vandermast, Oct 10 2008, Oct 14 2008

STATUS

approved

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Last modified October 21 14:33 EDT 2019. Contains 328301 sequences. (Running on oeis4.)