A344574 - OEIS

A344574

Number of ordered pairs (i,j) with 0 < i < j < n such that gcd(i,j,n) > 1.

0, 0, 0, 0, 0, 1, 0, 3, 1, 6, 0, 13, 0, 15, 7, 21, 0, 37, 0, 39, 16, 45, 0, 73, 6, 66, 28, 81, 0, 130, 0, 105, 46, 120, 21, 181, 0, 153, 67, 189, 0, 262, 0, 213, 118, 231, 0, 337, 15, 306, 121, 303, 0, 433, 51, 369, 154, 378, 0, 583, 0, 435, 217, 465

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,8

COMMENTS

A 4-regular circulant graph of order n, C(n,i,j), is connected if and only if gcd(n,i,j) = 1, where 0 < i < j < n.

LINKS

Table of n, a(n) for n=1..64.

Paul Theo Meijer, Connectivities and diameters of circulant graphs

Eric Weisstein's World of Mathematics, Circulant Graph

MATHEMATICA

npairs[n_]:=Module[{k=0},

Do[Do[