A366759 -id:A366759 - cp's OEIS frontend

A366760 a(n) = phi(n!+1), where phi is Euler's totient function (A000010).

1, 1, 2, 6, 20, 110, 612, 4970, 39600, 337680, 3298900, 39916800, 442155168, 6151996372, 83387930692, 1282826630160, 19089488332800, 355148307803520, 5427568925856000, 119931789135468100, 2432901890279317572, 49902667163053013232, 1073067539495604750240

Offset: 0

Sean A. Irvine, Oct 20 2023

nonn

Cf. A038507, A000010, A048855, A366759.

EulerPhi[Range[0,25]!+1] (* Paolo Xausa, Oct 21 2023 *)

PARI
```
{a(n) = eulerphi(n!+1)}
```

from math import factorial
from sympy import totient
def A366760(n): return totient(factorial(n)+1) # Chai Wah Wu, Oct 20 2023

a(n) = A000010(A038507(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.

Original entry on oeis.org

1, 4, 28, 180, 2308, 30028, 502080, 9458176, 215401680, 6387798300, 200559384576, 7369724839680, 304250263527208, 13082668722666720, 611670442764457840, 32588685419205242880, 1922760350056947598944, 117190066177425882515040, 7810108077410021826572976

Offset: 1

Sean A. Irvine, Oct 23 2023

nonn

Cf. A057588, A000010, A171989, A366759.

seq(numtheory[phi](mul(ithprime(k), k=1..n)-1), n=1..30);

PARI
```
a(n)=eulerphi(prod(k=1,n,prime(k))-1)
```

a(n) = A000010(A057588(n)).

cp's OEIS Frontend

A366760 a(n) = phi(n!+1), where phi is Euler's totient function (A000010).

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