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A174133 Integers of the form (a^2-1)*(b^2+1) where a >= 1 and b >= 0. 3

%I #18 May 05 2016 21:21:56

%S 0,3,6,8,15,16,24,30,35,40,48,51,63,70,75,78,80,96,99,111,120,126,136,

%T 143,150,160,168,175,195,198,208,224,240,246,255,286,288,296,303,315,

%U 323,336,350,360,366,390,399,400,408,435,440,448,480,483,495,510,520

%N Integers of the form (a^2-1)*(b^2+1) where a >= 1 and b >= 0.

%C Numbers of the form A002522(i)*A005563(j) where i,j >= 0. - _Altug Alkan_, May 02 2016

%H Robert Israel, <a href="/A174133/b174133.txt">Table of n, a(n) for n = 1..10000</a>

%e 3 is a term because 3 = (2^2-1)*(0^2+1).

%p N:= 10000: # to get all terms <= N

%p S:= {0, seq(seq((a^2-1)*(b^2+1), b=0 .. floor(sqrt(N/(a^2-1)-1))),a=2..floor(sqrt(N+1)))}:

%p sort(convert(S,list)); # _Robert Israel_, May 05 2016

%t TakeWhile[#, Function[k, k < Sqrt@ Max@ #]] &@ Select[DeleteDuplicates@ Sort[(#1^2 - 1) (#2^2 + 1) & @@@ Tuples[Range[0, 25], 2]], # >= 0 &] (* _Michael De Vlieger_, May 02 2016 *)

%Y Cf. A002522, A005563.

%K nonn

%O 1,2

%A _Max Alekseyev_, Apr 01 2010

%E Name clarified by _Altug Alkan_, May 02 2016

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Last modified April 25 05:18 EDT 2024. Contains 371964 sequences. (Running on oeis4.)