OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..100
FORMULA
a(n) = (1/n) * Sum_{d | n} totient(n/d) * A198635(d) / 2. - Andrew Howroyd, Mar 18 2017
EXAMPLE
All solutions for n=3:
..4....1....3....2....1....2....3....1....2....3....1....2
..5....2....4....3....2....3....4....2....3....4....2....3
..4....1....3....2....3....4....3....3....2....5....1....4
..5....2....4....3....2....3....4....4....3....4....2....5
..4....3....3....2....3....4....5....3....4....5....1....4
..5....2....4....3....2....3....4....2....3....4....2....3
MATHEMATICA
a[n_] := (1/n)*DivisorSum[n, EulerPhi[n/#] * (2*3^# + 2) &] / 2;
Array[a, 30] (* Jean-François Alcover, Oct 31 2017, after Andrew Howroyd *)
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 01 2012
EXTENSIONS
a(15)-a(30) from Andrew Howroyd, Mar 18 2017
STATUS
approved