A391355 Numbers k such that 4*k - (greatest prime < 4*k) = (least prime > 4*k) - 4*k.

1, 3, 14, 15, 16, 18, 19, 27, 30, 36, 40, 44, 45, 48, 57, 59, 60, 65, 72, 75, 78, 81, 87, 89, 94, 105, 108, 109, 133, 136, 138, 140, 149, 150, 151, 159, 164, 165, 170, 174, 184, 195, 198, 204, 207, 231, 236, 240, 245, 254, 255, 258, 259, 261, 264, 273, 275

Offset

1,2

Links

Table of n, a(n) for n=1..57.

Mathematica

z = 1500; f[x_] := f[x] = 4*x;
u[n_] := NextPrime[f[n], -1]; v[n_] := NextPrime[f[n]];
Select[Range[400], m*# - v[#] < u[#] - m*# &]    (* A391354 *)
Select[Range[400], m*# - v[#] == u[#] - m*# &]   (* A391355 *)
Select[Range[400], m*# - v[#] > u[#] - m*# &]    (* A391356 *)

Crossrefs

Cf. A000027, A000040, A391351, A391354, A391356.

Sequence in context: A171653 A055435 A242868 * A070418 A178363 A294997

Adjacent sequences: A391352 A391353 A391354 * A391356 A391357 A391358

Keyword

nonn

Author

Clark Kimberling, Dec 14 2025

Status

approved