面白い問題おしえて～な 28問目

面白い問題おしえて～ ..

632:１３２人目の素数さん
18/12/11 12:52:45.22 +jUDREv9.net
>>596-597
失礼。あってますね。orz
Prelude> let theAlpha k = k+1 - (sqrt $ k*(k+2))
Prelude> let theBeta k = k+1 + (sqrt $ k*(k+2))
Prelude> let x k n = let {alpha = theAlpha k; beta = theBeta k} in 1 + k*((beta^n -1)/(beta-1) - (alpha^n -1)/(alpha-1)) /(beta-alpha)
Prelude> let k = 1 in mapM_ print [x k n | n<-[0..9]]
1.0
1.0
2.0
6.0
21.0
77.0
286.0
1066.0
3977.0
14840.999999999996
Prelude> let y k = map head $ iterate (¥[u,v]->[v,(v)*(v+1)/(u)]) [1,1]
Prelude> let k = 1 in mapM_ print $ take 10 $ y k
1.0
1.0
2.0
6.0
21.0
77.0
286.0
1066.0
3977.0
14841.0

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