OFFSET
1,1
COMMENTS
If n is a Mersenne prime then a(n) = 3n (see comments in A000668).
MATHEMATICA
Table[EulerPhi[n]+DivisorSigma[1, DivisorSigma[1, n]], {n, 70}] (* Harvey P. Dale, Feb 27 2020 *)
PROG
(Magma) [EulerPhi(n) + SumOfDivisors(SumOfDivisors(n)) : n in [1..100]]; // Vincenzo Librandi, Nov 15 2014
(PARI) vector(100, n, eulerphi(n)+sigma(sigma(n))) \\ Derek Orr, Nov 15 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Omar E. Pol, Nov 14 2014
EXTENSIONS
Corrected and extended by Harvey P. Dale, Feb 27 2020
STATUS
approved