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A366810 a(n) = phi(prime(n)#-1) where phi is the Euler totient function and p# is the product of all the primes from 2 to p inclusive.

%I A366810 #5 Oct 24 2023 10:09:53
%S A366810 1,4,28,180,2308,30028,502080,9458176,215401680,6387798300,
%T A366810 200559384576,7369724839680,304250263527208,13082668722666720,
%U A366810 611670442764457840,32588685419205242880,1922760350056947598944,117190066177425882515040,7810108077410021826572976
%N A366810 a(n) = phi(prime(n)#-1) where phi is the Euler totient function and p# is the product of all the primes from 2 to p inclusive.
%F A366810 a(n) = A000010(A057588(n)).
%p A366810 seq(numtheory[phi](mul(ithprime(k), k=1..n)-1), n=1..30);
%o A366810 (PARI) a(n)=eulerphi(prod(k=1,n,prime(k))-1)
%Y A366810 Cf. A057588, A000010, A171989, A366759.
%K A366810 nonn
%O A366810 1,2
%A A366810 _Sean A. Irvine_, Oct 23 2023