OFFSET
1,2
COMMENTS
Let m be a superabundant number. Since m is a product of primorials P, we may identify a greatest primorial divisor P(omega(m)) = A002110(A001221(A004394(n))).
This sequence lists the primitive quotients k = m/P(omega(m)).
Since m is a product of primorials and k is the quotient resulting from division of m by the largest primorial divisor P, this sequence is also a subset of A025487, which in turn is a subset of A055932.
We can plot all m in A004394 at (A002110(j),k), but this sequence does not accommodate all highly composite numbers; it is missing k = {36, 96, 216, 480, ...}. In contrast, k in A301414 can represent all superabundant numbers m, but a(116)=592424239959167616000 is the least k missing. Therefore in order to plot both A002182 and A004394 one must use the union of a(n) and A301414(n). One can ably plot all the terms common to both A002182 and A004394 (i.e., A166981) using k in A301414.
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..2000
Michael De Vlieger, Annotated color-coded plot (x,y) = (a(n), A002110(j)) highlighting superabundant numbers.
Michael De Vlieger, Extended annotated color-coded plot showing all terms in A004394 that also appear in A224078.
Michael De Vlieger, Simple extended color-coded plot (x,y) = (a(n), A002110(m)) for coordinates between (1,0)..(225,379), with (1,0) in lower left corner.
EXAMPLE
Plot of (A002110(j),k) with k a term in this sequence such that A002110(j) * k is in A004394. Asterisks denote products that are in A004490.
{0,1} {1,1} {2,1}
1 2* 6*
{1,2} {2,2} {3,2}
4 12* 60*
{2,4} {3,4} {4,4}
24 120* 840
{2,6} {3,6} {4,6}
36 180 1260
{2,8} {3,8} {4,8}
48 240 1680
{3,12} {4,12} {5,12}
360* 2520* 27720
{3,24} {4,24} {5,24} {6,24}
720 5040* 55440* 720720*
{4,48} {5,48} {6,48}
10080 110880 1441440*
... ... ... ...
MATHEMATICA
Block[{s = Array[DivisorSigma[1, #]/# &, 10^6], t}, t = Union@ FoldList[Max, s]; Union@ Map[#/Product[Prime@ i, {i, PrimeNu@ #}] &@ First@ FirstPosition[s, #] &, t]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael De Vlieger, Dec 29 2020
STATUS
approved