OFFSET
0,5
LINKS
FORMULA
EXAMPLE
For n = 3, the 3rd primorial is 30, phi(30) = 8, a(3) = 1 since 1 is nonprime. See A048597.
For n = 4, the 4th primorial is 210, the size of its reduced residue system (RRS) is 48 of which 6 are either composite numbers or 1: {1, 121, 143, 169, 187, 209}.
MATHEMATICA
Table[Function[P, EulerPhi@ P - # &[PrimePi@ P - n]]@ Product[Prime@ i, {i, n}], {n, 0, 12}] (* Michael De Vlieger, May 08 2017 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
a(14)-a(15) from Max Alekseyev, Aug 21 2013
a(0) prepended, a(15) corrected, a(16)-a(17) computed from A000849 by Max Alekseyev, Feb 21 2016
a(18)-a(19) calculated using Kim Walisch's primecount and added by Amiram Eldar, Sep 03 2024
STATUS
approved