A063797 Numbers n such that sigma(d(n^3))==d(sigma(n^2)), where d(n) is the number of divisors of n.

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

Robert Israel, Table of n, a(n) for n = 1..200

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

Adjacent sequences: A063794 A063795 A063796 * A063798 A063799 A063800

Keyword

nonn

Author

Jason Earls, Aug 19 2001

Extensions

More terms from Robert Israel, Oct 22 2018

Status

approved