A391658 a(n) = A233671(n) - A046868(n).

-1, -1, -1, -2, -3, -2, -2, -2, -1, 1, 1, -1, 1, 1, -1, -1, -1, -1, 1, 2, 3, 3, 5, 4, 5, 9, 9, 8, 10, 10, 11, 11, 11, 9, 12, 10, 10, 7, 8, 9, 8, 6, 7, 6, 6, 7, 5, 6, 6, 7, 6, 8, 11, 13, 11, 13, 14, 13, 13, 14, 17, 19, 18, 19, 19, 17, 17, 17, 19, 19, 20, 20

Offset

1,4

Comments

Is a(n) < 0 for only finitely many n?

Links

Table of n, a(n) for n=1..72.

Formula

a(n) = A233671(n) - A046868(n).

Mathematica

z = 10000;
s1 = Select[Range[2, z], Prime[#]^2 > Prime[# - 1]*Prime[# + 1] &]; (* A046868 *)
s2 = Select[Range[2, z], Prime[#]^2 < Prime[# - 1]*Prime[# + 1] &]; (* A233671 *)
m = Min[{Length[s1], Length[s2]}];
Take[s2, m] - Take[s1, m]

Crossrefs

Cf. A000040, A046868, A233671.

Sequence in context: A286657 A334052 A160570 * A128830 A090387 A030329

Adjacent sequences: A391655 A391656 A391657 * A391659 A391660 A391661

Keyword

sign

Author

Clark Kimberling, Feb 10 2026

Status

approved