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Contents
# coding: utf-8
describe Integer, "#number_of_prime_factors" do
# http://www.research.att.com/~njas/sequences/A001222
BIGOMEGA = [0,1,1,2,1,2,1,3,2,2,1,3,1,2,2,4,1,3,1,3,2,2,1,4,
2,2,3,3,1,3,1,5,2,2,2,4,1,2,2,4,1,3,1,3,3,2,1,5,2,
3,2,3,1,4,2,4,2,2,1,4,1,2,3,6,2,3,1,3,2,3,1,5,1,2,
3,3,2,3,1,5,4,2,1,4,2,2,2,4,1,4,2,3,2,2,2,6,1,3,3,
4,1,3,1,4,3,2,1,5,1,3,2]
it "returns the number of prime factors (counted with multiplicity) of self" do
BIGOMEGA.each_with_index do |bigomega, number|
(number + 1).number_of_prime_factors.should == bigomega
end
end
it "is >= ω" do
BIGOMEGA.each_with_index do |bigomega, number|
(number + 1).number_of_prime_factors.should >= (number + 1).number_of_distinct_prime_factors
end
end
it "counts factors more than once" do
[4, 8, 9, 12, 16, 18, 20, 24, 25, 27, 28, 32, 36, 40, 44, 45, 48, 49,
50, 52, 54, 56, 60, 63, 64, 68, 72, 75, 76, 80, 81, 84, 88, 90, 92,
96, 98, 99, 100, 104, 108, 112, 116, 117, 120, 121, 124, 125, 126, 128,
132, 135, 136, 140, 144, 147, 148, 150].each do |number|
number.prime_factors.size.should >= 2
number.prime_factors.uniq.should_not == number.prime_factors
number.number_of_prime_factors.should == number.prime_factors.size
end
end
end
Version data entries
16 entries across 16 versions & 1 rubygems