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AlexVPopov/Project Euler 6b

Created September 24, 2013 12:34
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Project Euler 6b
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Project Euler 6b
# Sum of first n numbers is n(n+1)/2
# Sum of squares of first n numbers is n(n+1)(2n + 1)/6
# Expanded form for sum ^ 2 - sum of squares = n^4/4+n^3/6-n^2/4-n/6
def formula(n)
(n ** 4) / 4 + (n ** 3) / 6 - (n ** 2) / 4 - n / 6
end
p formula(100)
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