Search: id:A130205
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%I A130205
%S A130205 1,2,6,8,11,17,21,26,34,40,47,57,65,74,86,96,107,121,133,146,162,176,
%T A130205 191,209,225,242,262,280,299,321,341,362,386,408,431,457,481,506,534,
%U A130205 560,587,617,645,674,706,736,767,801,833,866,902,936,971,1009,1045,1082
%N A130205 a(n)=n^2-a(n-1)-a(n-2).
%C A130205 Any three consecutive terms sum up to a perfect square. First 9 terms 
               coincide with A076991.
%F A130205 a(1)=1, a(2)=2; n>2: a(n)=n^2-a(n-1)-a(n-2).
%F A130205 G.f.: x*(1+3*x^2-3*x^3+x^4)/(1+x+x^2)/(1-x)^3 [From Maksym Voznyy (voznyy(AT)mail.ru), 
               Jul 27 2009]
%e A130205 1+2+6=3^2, 2+6+8=4^2, 6+8+11=5^2.
%t A130205 a[1]=1;a[2]=2;a[n_]:=a[n]=n^2-a[n-1]-a[n-2]; Table[a[n],{n,100}]
%Y A130205 Cf. A076991, A130206.
%Y A130205 Sequence in context: A079418 A136496 A076991 this_sequence A054067 A064212 
               A056906
%Y A130205 Adjacent sequences: A130202 A130203 A130204 this_sequence A130206 A130207 
               A130208
%K A130205 nonn
%O A130205 1,2
%A A130205 Zak Seidov (zakseidov(AT)yahoo.com), May 16 2007
%E A130205 G.f. proposed by Maksym Voznyy checked and corrected by R. J. Mathar, 
               Sep 16 2009.

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