While we are playing this game, here it is in D: int total = recurrence!"n+1"(0) .map!(x => x*x) .take(10)

While we are playing this game, here it is in D: int total = recurrence!"n+1"(0) .map!(x => x*x) .take(10) .sum(); Replacing that last sum() with reduce() from std.parellelism and you can sum them using multiple threads (obviously not useful with a set this small but the documentation for reduce() coincidentally includes a benchmark for the sum of squares running 2.5x faster when done in parallel).