OFFSET
1,1
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..1000
A. Bogomolny, Euler Function and Theorem
P. A. MacMahon, Divisors of numbers and their continuations in the theory of partitions, Proc. London Math. Soc., 19 (1919), 75-113.
W. Sierpinski, Number Of Divisors And Their Sum
EXAMPLE
4 is in the sequence because tau(4) = 3, phi(3) = 2 and sopf(4) = 2.
8 is in the sequence because tau(8) = 4, phi(4) = 2 and sopf(8) = 2.
MAPLE
A008472 := proc(n) add(p, p= numtheory[factorset](n)) ; end proc:
A163109 := proc(n) numtheory[phi](numtheory[tau](n)) ; end proc:
for n from 1 to 40000 do if A008472(n) = A163109(n) then printf("%d, ", n); end if; end do: # R. J. Mathar, Sep 02 2011
MATHEMATICA
Select[Range[2, 50000], EulerPhi[DivisorSigma[0, #]]==Total[ Transpose[ FactorInteger[#]][[1]]]&] (* Harvey P. Dale, Nov 15 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 16 2010
EXTENSIONS
Corrected and edited by Michel Lagneau, Apr 25 2010
STATUS
approved