A210700 A047160(3n): smallest m >= 0 with both 3n - m and 3n + m prime.

0, 1, 2, 1, 2, 1, 2, 5, 4, 1, 4, 5, 2, 1, 2, 5, 8, 7, 4, 1, 4, 5, 2, 1, 4, 5, 2, 5, 14, 7, 4, 7, 2, 1, 2, 1, 2, 13, 10, 7, 14, 13, 2, 5, 4, 1, 10, 5, 10, 1, 4, 7, 8, 5, 2, 5, 8, 7, 4, 1, 10, 5, 8, 1, 2, 1, 10, 7, 16, 13, 14, 17, 8, 11, 2, 1, 2, 5, 4, 1, 14, 5

Offset: 1

Author

Jason Kimberley, Oct 15 2012

Keywords

• nonn
• easy

Comments

This sequence is interesting because, apart from a(2)=1, A155764 appears to consist only of multiples of three. Equivalently, since n and A047160(n) are coprime (for nonzero A047160(n)), no multiple of three appears to occur in A155765.

Links

• Jason Kimberley, Table of n, a(n) for n = 1..3333
• OEIS (Plot 2), Plot of (log(n), log(a(n)))
• OEIS (Plot 2), Plot of (log(A210701(n)), log(A210702(n)))

Crossrefs

Cf. A210701 (location of records in this sequence), A210702 (records in this sequence).

Programs

Mathematica

sml[n_]:=Module[{m=0},While[!PrimeQ[3n-m]||!PrimeQ[3n+m],m++];m]; Array[ sml,100] (* Harvey P. Dale, Sep 23 2022 *)