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"Rounded hypotenuses": a(n) = round(sqrt(a(n-1)^2 + a(n-2)^2)), a(1)=1, a(2)=3.
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%I #17 Oct 08 2018 03:46:26

%S 1,3,3,4,5,6,8,10,13,16,21,26,33,42,53,68,86,110,140,178,226,288,366,

%T 466,593,754,959,1220,1552,1974,2511,3194,4063,5168,6574,8362,10637,

%U 13530,17211,21892,27847,35422,45057,57314,72904,92736,117962,150050

%N "Rounded hypotenuses": a(n) = round(sqrt(a(n-1)^2 + a(n-2)^2)), a(1)=1, a(2)=3.

%H Chai Wah Wu, <a href="/A104804/b104804.txt">Table of n, a(n) for n = 1..2000</a>

%F a(n) = A063827(n) for n > 2. - _Georg Fischer_, Oct 07 2018

%t a[n_] := a[n] = Round[ Sqrt[ a[n - 1]^2 + a[n - 2]^2]]; a[1] = 1; a[2] = 3; Table[ a[n], {n, 48}] (* _Robert G. Wilson v_, Mar 28 2005 *)

%o (Python)

%o from gmpy2 import isqrt_rem

%o A104804_list = [1,3]

%o for _ in range(1000):

%o i, j = isqrt_rem(A104804_list[-1]**2+A104804_list[-2]**2)

%o A104804_list.append(int(i+ int(4*(j-i) >= 1))) # _Chai Wah Wu_, Aug 16 2016

%Y Cf. A104803, A104805.

%K nonn

%O 1,2

%A _Zak Seidov_, Mar 26 2005

%E More terms from _Robert G. Wilson v_, Mar 28 2005