OFFSET
1,5
LINKS
FORMULA
a(n) = Sum_{j=1..floor(n/3)} Sum_{i=j..floor((n-j)/2)} (1 - ceiling(n/j) + floor(n/j)).
MAPLE
f:= proc(n) local i, j;
add((floor((n-j)/2)-j+1), j = select(`<=`, numtheory:-divisors(n), n/3))
end proc:
map(f, [$1..100]); # Robert Israel, Sep 30 2024
MATHEMATICA
Array[Sum[Sum[(1 - Ceiling[#/j] + Floor[#/j]), {i, j, Floor[(# - j)/2]}], {j, Floor[#/3]}] &, 71] (* Michael De Vlieger, Oct 21 2021 *)
Table[Count[IntegerPartitions[n, {3}], _?(Divisible[n, #[[-1]]]&)], {n, 80}] (* Harvey P. Dale, Jul 10 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Oct 21 2021
STATUS
approved