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A173146
sigma(phi(n)) = rad(n), where phi(n)= Euler totient function, sigma(n)= sum of divisors of n, rad(n)= product of primes that divide n.
0
3, 15, 255, 2418, 65535, 110771178, 4294967295
OFFSET
1,1
LINKS
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972
EXAMPLE
Phi(3) = 2, sigma(2) = 3 and rad(3) = 3 Phi(15) = 8, sigma(8) = 15, and rad(15) = 15 3 = 3, 15 = 3.5, 255 = 3.5.17, 2418 = 2.3.13.31, 65535 = 3.5.17.257, 110771178 = 2.3.7.19.127.1093, 4294967295 = 3.5.17.257.65537
MAPLE
with(numtheory): for n from 1 to 5000000000 do : t1 := ifactors(n)[2] : t2 := mul(t1[i][1], i=1..nops(t1)): if sigma(phi(n)) = t2 then print (n): else fi : od :
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 11 2010
STATUS
approved