OFFSET
0,9
FORMULA
a(n) = Sum_{k=1..floor(n/4)} Sum_{j=k..floor((n-k)/3)} Sum_{i=j..floor((n-j-k)/2)} [j*i = k*(n-i-j-k)], where [ ] is the Iverson bracket.
MATHEMATICA
Table[Sum[Sum[Sum[KroneckerDelta[j*i, k*(n - i - j - k)], {i, j, Floor[(n - j - k)/2]}], {j, k, Floor[(n - k)/3]}], {k, Floor[n/4]}], {n, 0, 100}]
PROG
(PARI) for(n=0, 70, my(count=0); forpart(p=n, if(#p==4, count+=(p[1]*p[4]==p[2]*p[3]))); print1(count, ", ")) \\ Hugo Pfoertner, Jan 18 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jan 17 2021
STATUS
approved