Sum of divisors: Difference between revisions

=={{header|D}}==

{{trans|C}}

<lang d>import std.stdio;

// See https://en.wikipedia.org/wiki/Divisor_function

uint divisor_sum(uint n) {

uint total = 1, power = 2;

// Deal with powers of 2 first

for (; (n & 1) == 0; power <<= 1, n >>= 1) {

total += power;

}

// Odd prime factors up to the square root

for (uint p = 3; p * p <= n; p += 2) {

uint sum = 1;

for (power = p; n % p == 0; power *= p, n /= p) {

sum += power;

}

total *= sum;

}

// If n > 1 then it's prime

if (n > 1) {

total *= n + 1;

}

return total;

}

void main() {

immutable limit = 100;

writeln("Sum of divisors for the first ", limit," positive integers:");

for (uint n = 1; n <= limit; ++n) {

writef("%4d", divisor_sum(n));

if (n % 10 == 0) {

writeln;

}

}

}</lang>

{{out}}

<pre>Sum of divisors for the first 100 positive integers:

1 3 4 7 6 12 8 15 13 18

12 28 14 24 24 31 18 39 20 42

32 36 24 60 31 42 40 56 30 72

32 63 48 54 48 91 38 60 56 90

42 96 44 84 78 72 48 124 57 93

72 98 54 120 72 120 80 90 60 168

62 96 104 127 84 144 68 126 96 144

72 195 74 114 124 140 96 168 80 186

121 126 84 224 108 132 120 180 90 234

112 168 128 144 120 252 98 171 156 217 </pre>