OFFSET
1,1
MAPLE
A006862 := proc(n) if n = 0 then 2; else 1+mul(ithprime(j), j=1..n) ; end if: end proc: A171989 := proc(n) numtheory[phi](A006862(n)) ; end proc: seq(A171989(n), n=1..18) ; # R. J. Mathar, Jan 30 2010
PROG
(PARI) a(n)=eulerphi(prod(i=1, n, prime(i))+1) \\ Charles R Greathouse IV, Mar 05 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Teofilatto, Jan 21 2010
EXTENSIONS
a(1) inserted and extended beyond a(5) by R. J. Mathar, Jan 30 2010
STATUS
approved