A390511 a(n) = prime(A391807(n)).

7, 31, 151, 1753, 1747, 1741, 19471, 118801, 148537, 148531, 406951, 2339089, 2339041, 51662599, 51662593, 73451737, 232301497, 450988159, 1444257721, 1444257709, 1444257673, 24061965049, 24061965043, 43553959723, 43553959717, 502429570231, 1552841185993

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Mathematica

t = Table[Mod[Prime[nn], 3], {nn, 10^8}];  (* A039701 *)
u = Map[SequencePosition[t, Flatten[Join[{ConstantArray[1, #], 2}]], 1] &, Range[21]]
Prime[Table[First[Flatten[u[[n]]]], {n, 1, 21}]]
(* Peter J. C. Moses, Dec 11 2025 *)

Prog

(Python)
from sympy import nextprime, prime
from itertools import count, islice
def agen(NN=10000): # generator of terms for n <= NN
    n, pk, residues = 1, 1, "X"*NN
    for k in count(1):
        pk = nextprime(pk)
        resk = pk%3
        if resk == 2:
            while residues.endswith("1"*n) and n <= NN:
                yield prime(k-n)
                n += 1
        residues = residues[1:] + str(resk)
print(list(islice(agen(), 13))) # Michael S. Branicky, Jan 11 2026

Crossrefs

Cf. A000040, A391796, A391807.

Sequence in context: A121517 A199216 A057620 * A055625 A102239 A188233

Adjacent sequences: A390508 A390509 A390510 * A390512 A390513 A390514

Keyword

nonn

Author

Clark Kimberling, Jan 05 2026

Extensions

a(22)-a(25) from Michael S. Branicky, Jan 11 2026

a(26)-a(27) from Jinyuan Wang, Jan 16 2026

Status

approved