OFFSET
1,2
COMMENTS
max {n : a(n) > 0} = 32, a(n) = 0 for n > 32.
FORMULA
a(n) = max {99 < k < 1000 : A000005(k)=n} if set is nonempty, else a(n) = 0.
MAPLE
with (numtheory):
b:= n-> `if` (type (n, integer), n, 0):
a:= n-> b (max (select (x-> tau(x)=n, [$100..999])[])):
seq (a(n), n=1..60);
MATHEMATICA
digits=3; tbl=DivisorSigma[0, Range[10^(digits-1), 10^digits-1]]; t=Table[0, {Max[tbl]}]; offset=10^(digits-1)-1; Do[t[[tbl[[i]]]]=i+offset, {i, Length[tbl]}]; t
(With[{tb=Table[{n, DivisorSigma[0, n]}, {n, 999, 100, -1}]}, Table[ SelectFirst[ tb, #[[2]]==k&], {k, 60}]]/.Missing["NotFound"]->{0, 0}) [[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Nov 02 2019 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 27 2010
EXTENSIONS
Edited by Alois P. Heinz, Nov 27 2010
STATUS
approved