OFFSET
1,2
COMMENTS
Numbers n such that A181801(n) is higher than A181801(d) for any proper divisor d of n. Also, numbers n such that row n of A181802 is identical to no previous row of A181802.
A002182 is a proper subsequence of this sequence. 72 is the first LCM of some set of highly composite numbers that is not itself highly composite.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Achim Flammenkamp, List of the first 1200 highly composite numbers.
Eric Weisstein's World of Mathematics, Highly composite number.
Eric Weisstein's World of Mathematics, Least Common Multiple (LCM).
Eric Weisstein's World of Mathematics, Proper Divisor.
EXAMPLE
1, 2, 4, 6, 12, 24 and 36 are all highly composite numbers, and their least common multiple (LCM) is 72. Hence, 72 is a member of the sequence.
MATHEMATICA
seq[max_] := Module[{hcn = {}, hcnmax, d, dm = 0, s = {1}}, Do[d = DivisorSigma[0, n]; If[d > dm, dm = d; AppendTo[hcn, n]], {n, 1, max}]; hcnmax = hcn[[-1]]; Do[s = Union[Join[s, Select[LCM[hcn[[k]], s], # <= hcnmax &]]], {k, 2, Length[hcn]}]; s]; seq[300000] (* Amiram Eldar, Jun 23 2023 *)
KEYWORD
nonn
AUTHOR
Matthew Vandermast, Nov 27 2010
STATUS
approved