50 lines
1.8 KiB
VB.net
50 lines
1.8 KiB
VB.net
Imports System
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Module Program
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Function chowla(ByVal n As Integer) As Integer
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chowla = 0 : Dim j As Integer, i As Integer = 2
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While i * i <= n
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j = n / i : If n Mod i = 0 Then chowla += i + (If(i = j, 0, j))
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i += 1
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End While
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End Function
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Function sieve(ByVal limit As Integer) As Boolean()
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Dim c As Boolean() = New Boolean(limit - 1) {}, i As Integer = 3
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While i * 3 < limit
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If Not c(i) AndAlso (chowla(i) = 0) Then
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Dim j As Integer = 3 * i
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While j < limit : c(j) = True : j += 2 * i : End While
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End If : i += 2
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End While
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Return c
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End Function
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Sub Main(args As String())
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For i As Integer = 1 To 37
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Console.WriteLine("chowla({0}) = {1}", i, chowla(i))
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Next
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Dim count As Integer = 1, limit As Integer = CInt((10000000.0)), power As Integer = 100,
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c As Boolean() = sieve(limit)
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For i As Integer = 3 To limit - 1 Step 2
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If Not c(i) Then count += 1
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If i = power - 1 Then
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Console.WriteLine("Count of primes up to {0,10:n0} = {1:n0}", power, count)
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power = power * 10
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End If
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Next
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count = 0 : limit = 35000000
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Dim p As Integer, k As Integer = 2, kk As Integer = 3
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While True
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p = k * kk : If p > limit Then Exit While
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If chowla(p) = p - 1 Then
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Console.WriteLine("{0,10:n0} is a number that is perfect", p)
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count += 1
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End If
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k = kk + 1 : kk += k
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End While
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Console.WriteLine("There are {0} perfect numbers <= 35,000,000", count)
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If System.Diagnostics.Debugger.IsAttached Then Console.ReadKey()
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End Sub
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End Module
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