giles
87f9a84365
Some checks failed
Test, Build, and Deploy / test-build-deploy (push) Failing after 23s
div_sum computes proper divisor sum via trial division up to sqrt(n):
let div_sum n =
let s = ref 1 in
let i = ref 2 in
while !i * !i <= n do
if n mod !i = 0 then begin
s := !s + !i;
let q = n / !i in
if q <> !i then s := !s + q
end;
i := !i + 1
done;
if n = 1 then 0 else !s
Outer loop finds amicable pairs (a, b) with d(a) = b, d(b) = a,
a != b. Only pair under 300 is (220, 284); 220 + 284 = 504.
Real PE21 uses 10000 (answer 31626). 300 keeps the run under
budget while exercising the same divisor-sum trick.
119 baseline programs total.