A391042 Row lengths of A391041.

2, 2, 3, 3, 2, 3, 3, 3, 5, 3, 3, 4, 3, 3, 5, 3, 2, 6, 2, 4, 4, 4, 3, 5, 3, 3, 6, 5, 3, 6, 2, 3, 5, 3, 4, 7, 3, 2, 5, 4, 3, 4, 3, 5, 8, 3, 2, 6, 4, 4, 4, 4, 3, 7, 2, 5, 4, 4, 2, 8, 2, 2, 7, 4, 4, 6, 3, 3, 6, 6, 2, 8, 3, 3, 7, 3, 4, 6, 3, 4, 7, 3, 3, 7, 2, 3, 5, 6, 3, 10

Offset

1,1

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Stephen McKean, Toda primes, arXiv:2511.19744 [math.NT], 2025.

Mathematica

A391042[n_] := With[{m = 4*n}, Count[Prime[Range[2, PrimePi[m + 1]]], _?(Divisible[m, # - 1] && CoprimeQ[#, m/(# - 1)] &)]];
Array[A391042, 100] (* Paolo Xausa, Nov 26 2025 *)

Crossrefs

Cf. A391041.

Sequence in context: A110012 A233542 A375802 * A391038 A245908 A023514

Adjacent sequences: A391039 A391040 A391041 * A391043 A391044 A391045

Keyword

nonn

Author

Michel Marcus, Nov 26 2025

Status

approved