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A063797
Numbers n such that sigma(d(n^3))==d(sigma(n^2)), where d(n) is the number of divisors of n.
1
1, 961, 1369, 2209, 2809, 3721, 7921, 9409, 11881, 12769, 17161, 18769, 22201, 24649, 27889, 32761, 38809, 44521, 58081, 73441, 80089, 94249, 96721, 100489, 109561, 121801, 134689, 143641, 146689, 151321, 167281, 187489, 196249, 249001, 292681, 326041, 332929, 344569, 351649, 358801, 375769
OFFSET
1,2
COMMENTS
Not all a(n) are 1 mod 24. First counterexample is 5036684. But for a prime p, with sigma(p^4) squarefree and omega(sigma(p^4)==3, p^2 is in a(n). For these primes (as for all primes > 3), p^2 = 1 mod 24. - Lambert Herrgesell (lambert.herrgesell(AT)googlemail.com), Jan 08 2007, edited by Robert Israel, Oct 22 2018.
LINKS
MAPLE
filter:= proc(n) uses numtheory: sigma(tau(n^3))=tau(sigma(n^2)) end proc:
select(filter, [$1..10^6]); # Robert Israel, Oct 22 2018
PROG
(PARI) for(n=1, 10^7, if(sigma(numdiv(n^3))==numdiv(sigma(n^2)), print(n)))
CROSSREFS
Sequence in context: A166964 A316337 A274120 * A231761 A098207 A304315
KEYWORD
nonn
AUTHOR
Jason Earls, Aug 19 2001
EXTENSIONS
More terms from Robert Israel, Oct 22 2018
STATUS
approved