OFFSET
1,1
COMMENTS
From Robert Israel, Nov 07 2016: (Start)
If m is in A023194, sigma(m)^(m-1) is in the sequence.
If p and q are distinct primes, and r and s are distinct primes such that r+s = (p+1)(q+1), then r^(p-1)*s^(q-1) is in the sequence.
(End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..1000
C. K. Caldwell, The Prime Glossary, Number of divisors
P. A. MacMahon, Divisors of numbers and their continuations in the theory of partitions, Proc. London Math. Soc., 19 (1921), 75-113.
W. Sierpinski, Number Of Divisors And Their Sum
EXAMPLE
MAPLE
with(numtheory): for n from 1 to 100000 do : t1:= ifactors(n)[2] : t2 :=sum(t1[i][1], i=1..nops(t1)):if sigma(tau(n)) = t2 then print (n): else fi : od :
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 16 2010
EXTENSIONS
"sopf" uses replaced and examples disentangled by R. J. Mathar, Feb 24 2010
STATUS
approved