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%I #29 Jul 27 2021 05:02:36
%S 0,24,120,6240,30624,1585080,7778520,402604224,1975713600,
%T 102259887960,501823476024,25973608937760,127461187196640,
%U 6597194410303224,32374639724470680,1675661406608081280,8223031028828356224,425611400084042342040,2088617506682678010360
%N Numbers k such that both k+1 and 7k+1 are squares.
%H Harvey P. Dale, <a href="/A195917/b195917.txt">Table of n, a(n) for n = 1..832</a>
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,254,-254,-1,1).
%F a(n) = A161852(n)^2-1. - _Bruno Berselli_, Oct 28 2011
%F G.f.: -24*x^2*(1+4*x+x^2) / ( (x-1)*(x^2-16*x+1)*(x^2+16*x+1) ). - _R. J. Mathar_, Nov 04 2011
%t LinearRecurrence[{1,254,-254,-1,1},{0,24,120,6240,30624},20] (* _Harvey P. Dale_, Apr 01 2020 *)
%Y Cf. A195878, A161852.
%K nonn,easy
%O 1,2
%A _Sture Sjöstedt_, Oct 26 2011
%E More terms from _Bruno Berselli_, Oct 28 2011
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