OFFSET
1,2
COMMENTS
Sequence of numbers k(n): 2, 31, 101, 319, 73660, 118579, …
Conjecture: Subsequence of A216793.
Refactorable multiply-perfect numbers (A245782) are members of this sequence.
a(12) > 10^13. - Giovanni Resta, Jul 13 2015
FORMULA
A245785(a(n)) = 1.
EXAMPLE
672 is in sequence because 672/tau(672) + sigma(672)/672 = 672/24 + 2016/672 = 31 (integer).
PROG
(Magma) [n: n in [1..100000] | (Denominator((n/(#[d: d in Divisors(n)])) + (SumOfDivisors(n)/n)) eq 1)]
(PARI) for(n=1, 10^8, s=n/numdiv(n); t=sigma(n)/n; if(floor(s+t)==s+t, print1(n, ", "))) \\ Derek Orr, Aug 15 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Aug 15 2014
EXTENSIONS
a(7)-a(11) from Giovanni Resta, Jul 13 2015
STATUS
approved