OFFSET
1,1
COMMENTS
Conjecture: all natural numbers 1,2,3,...,n will eventually occur among the integer values of sigma(phi(n))/sigma(n).
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..370
EXAMPLE
a(1) = 121679 because sigma(phi(121679))/sigma(121679) = 4.
MAPLE
for n from 1 do spn := numtheory[sigma](numtheory[phi](n)) ; sn := numtheory[sigma](n) ; if spn mod sn = 0 then if spn/sn >= 4 then print(n, spn/sn) fi; fi; od: # R. J. Mathar, Oct 01 2008
PROG
(PARI) { n=0; for (m=1, 10^10, if((e=sigma(eulerphi(m))) % (s=sigma(m)) == 0 && e/s >= 4, write("b066881.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Apr 03 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Earls, Jan 22 2002
EXTENSIONS
Terms a(16) etc. from R. J. Mathar, Oct 01 2008
STATUS
approved