OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..80
EXAMPLE
All solutions for n=3:
.-2...-1...-2...-3...-3...-2....0...-1...-1...-2...-3...-3...-2
..0....1....3....2....1....1....0....0...-1....2....0....3...-1
..2....0...-1....1....2....1....0....1....2....0....3....0....3
MATHEMATICA
comps[r_, m_, k_] := Sum[(-1)^i*Binomial[r - 1 - i*m, k - 1]*Binomial[k, i], {i, 0, Floor[(r - k)/m]}]; a[n_, k_] := DivisorSum[n, EulerPhi[n/#] comps[#*(k + 1), 2 k + 1, #] &]/n; a[n_] := a[n, n]; Array[a, 18] (* Jean-François Alcover, Nov 01 2017, after Andrew Howroyd *)
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 29 2012
EXTENSIONS
a(12)-a(18) from Andrew Howroyd, Mar 02 2017
STATUS
approved