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A296079
a(n) = 1 if 1+phi(n) is prime, 0 otherwise, where phi = A000010, Euler totient function.
6
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0
OFFSET
1,1
COMMENTS
Out of the first 65537 values, 26197 are 1's (indicating primes), and 39340 are 0's, indicating nonprimes.
FORMULA
a(n) = A010051(A039649(n)) = A010051(1+A000010(n)).
For all n, a(n) >= A010051(n) and a(2n) >= A010051(n).
MATHEMATICA
Table[If[PrimeQ[EulerPhi[n]+1], 1, 0], {n, 120}] (* Harvey P. Dale, Apr 23 2020 *)
PROG
(PARI) A296079(n) = isprime(1+eulerphi(n));
CROSSREFS
Characteristic function of A039698.
Cf. A039689 (positions of zeros).
Cf. also A296077, A296078, A296080.
Sequence in context: A014451 A106667 A133011 * A354806 A340363 A340372
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 05 2017
STATUS
approved