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- #!/usr/bin/ruby
- # Arithmetical convolution of two functions.
- # See also:
- # https://en.wikipedia.org/wiki/Convolution
- func convolution(n, f, g) {
- sum(1..n, {|k|
- f(k) * g(n - k + 1)
- })
- }
- # Example:
- # Convolution of sigma(n) (A000203) with phi(n) (A000010).
- var f = { .sigma }
- var g = { .euler_phi }
- say 20.of {|n| convolution(n, f, g) } # https://oeis.org/A086733
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