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A332219
a(n) = 1 if 2^n - 1 is a prime, 0 otherwise.
2
0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
1
FORMULA
a(n) = A010051(A000225(n)).
a(n) <= A010051(n).
MATHEMATICA
Array[Boole@ PrimeQ[2^# - 1] &, 107] (* Michael De Vlieger, Feb 09 2020 *)
PROG
(PARI) A332219(n) = (isprime(n)&&isprime((2^n)-1));
CROSSREFS
Characteristic function of Mersenne exponents, A000043.
Cf. A000225, A010051, A332220 (partial sums).
Sequence in context: A118247 A286487 A122257 * A227625 A373497 A129950
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 09 2020
STATUS
approved