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A096783 Numbers n such that n, n+1, n+2, n+3, n+4 are all of the form x^2+2*y^2 for nonnegative x, y. 1

%I #6 Mar 28 2015 22:16:42

%S 0,96,800,2400,3200,3648,4096,4800,6272,7296,9600,18272,19648,20000,

%T 20672,23648,28224,28800,29472,31424,34848,36896,37472,43072,48672,

%U 50272,51200,53600,53824,55072,57696,59648,62848,64800,66048,69824

%N Numbers n such that n, n+1, n+2, n+3, n+4 are all of the form x^2+2*y^2 for nonnegative x, y.

%e 96=8^2+2*4^2, 97=5^2+2*6^2, 98 = 0^2+2*7^2,99=9^2+2*3^2=7^2+2*5^2,100=10^2+2*0^2

%t f[n_] := f[n_] = Block[{y = 0}, While[x = Sqrt[n - 2y^2]; !IntegerQ[x] && x >= 0, y++ ]; If[x \[Element] Reals, 1, 0]]; Select[ Range[0, 76895], f[ # ] == f[ # + 1] == f[ # + 2] == f[ # + 3] == f[ # + 4] == 1 &] (* _Robert G. Wilson v_, Aug 20 2004 *)

%K nonn

%O 1,2

%A _John L. Drost_, Aug 16 2004

%E More terms from _Robert G. Wilson v_, Aug 20 2004

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)