Data commit

Task/Chowla-numbers/Nim/chowla-numbers.nim

@@ -0,0 +1,43 @@
+import strformat
+import strutils
+
+func chowla(n: uint64): uint64 =
+  var sum = 0u64
+  var i = 2u64
+  var j: uint64
+  while i * i <= n:
+    if n mod i == 0:
+      j = n div i
+      sum += i
+      if i != j:
+        sum += j
+    inc i
+  sum
+
+for n in 1u64..37:
+  echo &"chowla({n}) = {chowla(n)}"
+
+var count = 0
+var power = 100u64
+for n in 2u64..10_000_000:
+  if chowla(n) == 0:
+    inc count
+  if n mod power == 0:
+    echo &"There are {insertSep($count, ','):>7} primes < {insertSep($power, ','):>10}"
+    power *= 10
+
+count = 0
+const limit = 350_000_000u64
+var k = 2u64
+var kk = 3u64
+var p: uint64
+while true:
+  p = k * kk
+  if p > limit:
+    break
+  if chowla(p) == p - 1:
+    echo &"{insertSep($p, ','):>10} is a perfect number"
+    inc count
+  k = kk + 1
+  kk += k
+echo &"There are {count} perfect numbers < {insertSep($limit, ',')}"