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A099618
a(n) = 1 if the n-th prime == 1 mod 6, otherwise a(n) = 0.
4
0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1
OFFSET
1,1
FORMULA
From Amiram Eldar, Mar 14 2025: (Start)
a(n) = 1 - A132194(m).
Sum_{k=1..n} a(k) ~ n / 2. (End)
MATHEMATICA
Table[Mod[Mod[Mod[Mod[Prime[k], 6], 5], 3], 2], {k, 1, 120}]
a[n_] := Boole[Mod[Prime[n], 6] == 1]; Array[a, 120] (* Amiram Eldar, Mar 14 2025 *)
PROG
(PARI) a(n) = (prime(n) % 6) == 1; \\ Michel Marcus, Jun 26 2019
CROSSREFS
Characteristic function of A091178.
Sequence in context: A341609 A064911 A174898 * A361496 A360125 A324883
KEYWORD
nonn,easy,changed
AUTHOR
Joseph Biberstine (jrbibers(AT)indiana.edu), Nov 19 2004
STATUS
approved