OFFSET
0,13
FORMULA
a(n) = Sum_{k=1..floor(n/4)} Sum_{j=k..floor((n-k)/3)} Sum_{i=j..floor((n-j-k)/2)} [k*(k+1) = n-i-j], where [ ] is the Iverson bracket.
MATHEMATICA
Table[Sum[Sum[Sum[KroneckerDelta[k*(k + 1), n - i - j], {i, j, Floor[(n - j - k)/2]}], {j, k, Floor[(n - k)/3]}], {k, Floor[n/4]}], {n, 0, 100}]
Table[Count[IntegerPartitions[n, {4}], _?(#[[1]]==#[[-1]]^2&)], {n, 0, 90}] (* Harvey P. Dale, May 22 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jan 06 2021
STATUS
approved