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A282472
Numbers k where records occur for d(k^2)/d(k), where d(k) is A000005(k).
3
1, 2, 4, 6, 12, 24, 30, 60, 120, 180, 210, 420, 840, 1260, 2310, 4620, 9240, 13860, 27720, 30030, 60060, 120120, 180180, 360360, 510510, 1021020, 2042040, 3063060, 6126120, 9699690, 19399380, 38798760, 58198140, 116396280, 223092870, 446185740, 892371480
OFFSET
1,2
COMMENTS
First 14 terms are similar, with A168264.
The quotients are (1, 3/2, 5/3, 9/4, 5/2, 21/8, 27/8, 15/4, 63/16, 25/6, 81/16, 45/8, 189/32, 25/4, 243/32, 135/16, 567/64, 75/8, 315/32, 729/64, 405/32, 1701/128, 225/16, 945/64, 2187/128, 1215/64, 5103/256, 675/32, 2835/128, 6561/256, 3645/128, 15309/512, 2025/64, 8505/256, 19683/512,...). - Lars Blomberg, Apr 10 2017
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..176 (terms 1..50 from Giovanni Resta)
MAPLE
A282472 := proc(n)
option remember;
local a, a1, rec ;
if n = 1 then
1;
else
a1 := procname(n-1) ;
rec := numtheory[tau](a1^2)/numtheory[tau](a1) ;
for a from a1+1 do
if numtheory[tau](a^2)/numtheory[tau](a) > rec then
return a;
end if;
end do:
end if;
end proc: # R. J. Mathar, Mar 03 2017
MATHEMATICA
s={}; rm=0; Do[r=DivisorSigma[0, n^2]/DivisorSigma[0, n]; If[r > rm, rm = r; AppendTo[s, n]], {n, 1, 10^4}]; s (* Amiram Eldar, Jul 17 2019 *)
PROG
(Perl)
use ntheory qw(:all);
for (my ($n, $m) = (1, 0) ; ; ++$n) {
my $d = divisors($n*$n) / divisors($n);
if ($m < $d) {
$m = $d;
print "$n\n";
}
}
(PARI) lista(nn) = {rec = 0; for (n=1, nn, if ((newrec = numdiv(n^2)/numdiv(n)) > rec, rec = newrec; print1(n, ", ")); ); } \\ Michel Marcus, Feb 20 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Daniel Suteu, Feb 18 2017
EXTENSIONS
a(32)-a(35) from Lars Blomberg, Apr 10 2017
a(36)-a(37) from Giovanni Resta, Apr 10 2017
STATUS
approved