giles
da96a79104
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A number n is abundant if its proper-divisor sum exceeds n. Reuses
the trial-division div_sum helper:
let count_abundant n =
let c = ref 0 in
for i = 12 to n - 1 do
if div_sum i > i then c := !c + 1
done;
!c
count_abundant 100 = 21
Abundant numbers under 100, starting at 12, 18, 20, 24, 30, 36, 40,
42, 48, 54, 56, 60, 66, 70, 72, 78, 80, 84, 88, 90, 96 -> 21.
Companion to euler21_small.ml (amicable). The classification:
perfect: d(n) = n (e.g. 6, 28)
abundant: d(n) > n (e.g. 12, 18)
deficient:d(n) < n (everything else)
124 baseline programs total.
24 lines
389 B
OCaml
24 lines
389 B
OCaml
let div_sum n =
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let s = ref 1 in
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let i = ref 2 in
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while !i * !i <= n do
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if n mod !i = 0 then begin
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s := !s + !i;
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let q = n / !i in
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if q <> !i then s := !s + q
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end;
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i := !i + 1
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done;
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if n = 1 then 0 else !s
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let count_abundant n =
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let c = ref 0 in
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for i = 12 to n - 1 do
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if div_sum i > i then c := !c + 1
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done;
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!c
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;;
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count_abundant 100
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