OFFSET
1,2
COMMENTS
If n is prime or semiprime, then a(n) = 2n-2.
FORMULA
a(n) = 2n - 2 + A153011(n). - Omar E. Pol, May 20 2015
MATHEMATICA
Table[DivisorSigma[1, n] + EulerPhi[n] - DivisorSigma[0, n], {n, 100}]
PROG
(PARI) vector(100, n, sigma(n)+eulerphi(n)-numdiv(n)) \\ Derek Orr, May 05 2015
(Magma) [SumOfDivisors(n)+ EulerPhi(n)-NumberOfDivisors(n): n in [1..100]]; // Vincenzo Librandi, May 06 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, May 05 2015
STATUS
approved