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%I #18 Jul 27 2021 12:09:46
%S 1,8,50,276,1397,6672,30565,135668,587426,2493056,10407393,42848800,
%T 174348417,702245128,2803634370,11106624804,43697519013,170871040752,
%U 664492915061,2571316718500,9905232077842,38000679280352,145240335213857,553203971301184,2100403987129441,7951405959127848
%N COMPOSE squares with squares.
%H N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%H <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (12, -54, 115, -132, 108, -59, 24, -6, 1).
%F G.f.: ((1-x)^3*(1+x)*(1-2*x+4*x^2-x^3))/((1-4*x+2*x^2-x^3)^3).
%F a(n) = 12*a(n-1)-54*a(n-2)+115*a(n-3)-132*a(n-4)+108*a(n-5)-59*a(n-6)+24*a(n-7)-6*a(n-8)+a(n-9). - _Wesley Ivan Hurt_, Apr 23 2021
%t CoefficientList[Series[((1-x)^3(1+x)(1-2x+4x^2-x^3))/((1-4x+2x^2-x^3)^3),{x,0,30}],x] (* or *) LinearRecurrence[{12,-54,115,-132,108,-59,24,-6,1},{1,8,50,276,1397,6672,30565,135668,587426},30] (* _Harvey P. Dale_, Mar 14 2016 *)
%o (PARI) Vec(((1-x)^3*(1+x)*(1-2*x+4*x^2-x^3))/((1-4*x+2*x^2-x^3)^3)+O(x^66)) \\ _Joerg Arndt_, Apr 21 2013
%Y Cf. A000290, A030267, A279282.
%K nonn,nice,easy
%O 1,2
%A _Christian G. Bower_
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