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%I #44 Jul 31 2022 19:53:27
%S 4,9,16,20,25,35,36,49,54,56,60,64,77,80,81,91,99,100,104,108,110,121,
%T 128,135,136,140,143,144,154,156,169,170,171,176,180,182,187,189,195,
%U 196,209,216,220,221,224,225,240,250,252,256,260,266,270,272,275,286,289
%N Numbers of the form (ab+cd)*(ad+bc) with integers a,b,c,d >= 1.
%H David A. Corneth, <a href="/A355854/b355854.txt">Table of n, a(n) for n = 1..10000</a>
%e 77 is in the sequence because (1*1+2*5)(1*5+1*2)=77 (for a=1, b=1, c=2, d=5).
%Y Cf. A000290.
%K nonn
%O 1,1
%A _Thomas Kerscher_, Jul 30 2022
%E More terms from _David A. Corneth_, Jul 30 2022
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