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- #!/usr/bin/ruby
- # Daniel "Trizen" Șuteu
- # Date: 21 September 2019
- # https://github.com/trizen
- # https://projecteuler.net/problem=133
- # Runtime: 0.335s
- # See also:
- # https://oeis.org/A178070
- var limit = 100_000
- var N = ipow10(limit.ilog2)
- var P = Set(primes(7, limit).grep {|p| znorder(10, p) `divides` N }...)
- say limit.primes.grep { !P.has(_) }.sum
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