OFFSET
1,4
REFERENCES
George E. Andrews, "Number Theory," Dover Publ., NY, 1971, page 85.
MATHEMATICA
Do[Print[Mod[DivisorSigma[1, n]*EulerPhi[n] + 1, n]], {n, 1, 100}] Note that iff n is a prime then Sigma(n)*Phi(n) + 1 = 0 (Mod n).
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Jul 28 2000
STATUS
approved