A171989 - OEIS

A171989

a(n) = A000010(A006862(n)).

2, 6, 30, 210, 2310, 29464, 476928, 9671392, 222388792, 6438663000, 200560490130, 7379606916000, 299261862900000, 13004421443456272, 614231422273479360, 31727029501157817600, 1915248189055217892480, 116762424492324428512272

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..18.

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

Cf. A000010, A006862.

Sequence in context: A377877 A096775 A331665 * A335069 A361807 A233438

Adjacent sequences: A171986 A171987 A171988 * A171990 A171991 A171992

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