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A172042
a(n) = A000010(A083553(n)).
1
1, 4, 8, 16, 32, 64, 96, 120, 240, 192, 288, 384, 384, 528, 1056, 1344, 896, 960, 960, 1152, 1728, 1920, 3200, 2560, 2560, 2560, 3328, 3744, 3456, 4032, 3456, 6144, 5632, 6336, 5760, 5760, 7776, 8856, 13776, 14784, 8448, 8640, 9216, 10752, 10080, 8640
OFFSET
1,2
COMMENTS
Except for the first term, a(n) is divisible by 4.
LINKS
MAPLE
A083553 := proc(n) (ithprime(n+1)-1)*(ithprime(n)-1) ; end proc: A172042 := proc(n) numtheory[phi](A083553(n)) ; end proc: seq(A172042(n), n=1..80) ; # R. J. Mathar, Jan 30 2010
MATHEMATICA
Table[EulerPhi[(Prime[n + 1] - 1)*(Prime[n] - 1)], {n, 1, 50}] (* Amiram Eldar, Apr 09 2021 *)
PROG
(PARI) a(n)=my(p=prime(n)); eulerphi((p-1)*(nextprime(p+1)-1)) \\ Charles R Greathouse IV, Mar 05 2013
CROSSREFS
Sequence in context: A036313 A121986 A285906 * A352918 A145108 A108569
KEYWORD
easy,nonn
AUTHOR
Giovanni Teofilatto, Jan 24 2010
EXTENSIONS
a(2) inserted and terms beyond a(10) added by R. J. Mathar, Jan 30 2010
STATUS
approved