hyuki/a.rb

## a.rb
# N!を素因数分解したときの2の指数について
# cf. https://twitter.com/numachi11111/status/1315844576851050497
# See also: https://oeis.org/A011371
def f(n)
  if n == 0
    1
  else
    n * f(n-1)
  end
end

def e(n)
  e = 0
  while n % 2 == 0
    e += 1
    n /= 2
  end
  e
end

1000.times do |n|
  a = n
  s = 0
  loop do
    a = a / 2
    s += a
    break if a == 0
  end
  puts "N = #{n} : #{s} #{e(f(n))}"
end
	# N!を素因数分解したときの2の指数について
	# cf. https://twitter.com/numachi11111/status/1315844576851050497
	# See also: https://oeis.org/A011371
	def f(n)
	if n == 0
	1
	else
	n * f(n-1)
	end
	end

	def e(n)
	e = 0
	while n % 2 == 0
	e += 1
	n /= 2
	end
	e
	end

	1000.times do \|n\|
	a = n
	s = 0
	loop do
	a = a / 2
	s += a
	break if a == 0
	end
	puts "N = #{n} : #{s} #{e(f(n))}"
	end