login
A210594
"Factor-dense" numbers: integers n where (# of proper divisors of n) / log(n) sets a new record.
3
2, 6, 12, 24, 36, 48, 60, 120, 180, 240, 360, 720, 840, 1260, 1680, 2520, 5040, 7560, 10080, 15120, 20160, 25200, 27720, 50400, 55440, 83160, 110880, 166320, 221760, 277200, 332640, 498960, 554400, 665280, 720720, 1081080, 1441440, 2162160, 2882880, 3603600
OFFSET
1,1
COMMENTS
Let d(n) = the number of proper divisors of n (A032741).
Define the "factor density" of n as f(n) = d(n) / log(n).
n is "factor dense" if f(m) < f(n) for all integers m where 2 <= m < n.
Missing highly-composite numbers (A002182) are 4 and 45360.
An alternative definition of factor density is g(n) = tau(n) / log(1+n), where tau(n) is the total number of divisors of n (A000005). Then records for g(n) appear to be set at all members of this sequence together with 1 and 4. - Hal M. Switkay, Sep 07 2022
LINKS
MATHEMATICA
f[n_] := N[(DivisorSigma[0, n] - 1)/Log[n]]; mx = 0; lst = {}; Do[ If[ f[n] > mx, mx = f[n]; AppendTo[lst, n]], {n, 2, 4000000, 2}]; t (* T. D. Noe, Mar 23 2012 *)
PROG
(PARI) lista(nn) = {my(m=0); for (n=2, nn, my(mm = (numdiv(n)-1)/log(n)); if (mm > m, print1(n, ", "); m = mm); ); } \\ Michel Marcus, Sep 08 2022
CROSSREFS
Cf. A189686.
Sequence in context: A099993 A011778 A067718 * A307252 A306625 A262986
KEYWORD
nonn
AUTHOR
Daniel Bishop, Mar 23 2012
STATUS
approved