OFFSET
0,8
FORMULA
a(n) = Sum_{k=1..floor(n/4)} Sum_{j=k..floor((n-k)/3)} floor(1/gcd(k,j)) * Sum_{i=j..floor((n-j-k)/2)} floor(1/gcd(i,n-i-j-k)).
MATHEMATICA
Table[Sum[Sum[Sum[Floor[1/GCD[k, j]]*Floor[1/GCD[i, n - i - j - k]], {i, j, Floor[(n - j - k)/2]}], {j, k, Floor[(n - k)/3]}], {k, Floor[n/4]}], {n, 0, 80}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jan 19 2021
STATUS
approved