A296079 a(n) = 1 if 1+phi(n) is prime, 0 otherwise, where phi = A000010, Euler totient function.

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.

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

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

Adjacent sequences: A296076 A296077 A296078 * A296080 A296081 A296082

Keyword

nonn

Author

Antti Karttunen, Dec 05 2017

Status

approved