A392104 - OEIS

%I #16 Jan 17 2026 12:56:33

%S 5,23,47,251,1889,7793,43451,243161,726893,759821,1820123,1820111,

%T 10141499,19725479,19725473,136209239,400414127,400414121,489144659,

%U 489144599,766319201,766319189,21549657581,21549657551,21549657539,140432294399,140432294381,437339303279

%N a(n) = prime(A391796(n)).

%t t = Table[Mod[Prime[nn], 3], {nn, 10^8}]; (* A039701 *)

%t u = Map[SequencePosition[t, Flatten[Join[{ConstantArray[2, #], 1}]], 1] &, Range[21]]

%t Prime[Table[First[Flatten[u[[n]]]], {n, 1, 21}]]

%t (* _Peter J. C. Moses_, Dec 11 2025 *)

%o (Python)

%o from sympy import nextprime, prime

%o from itertools import count, islice

%o def agen(NN=10000): # generator of terms for n <= NN

%o     n, pk, residues = 1, 1, "X"*NN

%o     for k in count(1):

%o         pk = nextprime(pk)

%o         resk = pk%3

%o         if resk == 1:

%o             while residues.endswith("2"*n) and n <= NN:

%o                 yield prime(k-n)

%o                 n += 1

%o         residues = residues[1:] + str(resk)

%o print(list(islice(agen(), 12))) # _Michael S. Branicky_, Jan 11 2026

%Y Cf. A391796, A391807.

%K nonn

%O 1,1

%A _Clark Kimberling_, Jan 08 2026

%E a(22)-a(27) from _Michael S. Branicky_, Jan 11 2026

%E a(28) from _Jinyuan Wang_, Jan 16 2026