|
%I #13 Oct 22 2019 11:32:23
%S 1,9,73,289,801,1801,3529,6273,10369,16201,24201,34849,48673,66249,
%T 88201,115201,147969,187273,233929,288801,352801,426889,512073,609409,
%U 720001,845001,985609,1143073,1318689,1513801,1729801,1968129,2230273
%N Middle term of a triple of consecutive numbers which are sums of two squares.
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F a(n)=8*A000537(n) + 1.
%F a(n)=1+2*n^2+4*n^3+2*n^4. G.f.: -(x^4+4*x^3+38*x^2+4*x+1)/(x-1)^5. [_Colin Barker_, Jul 28 2012]
%e 1801 is in the sequence because we may for instance write 1800 = 6^2 + 42^2; 1801 = 24^2 + 35^2; 1802 = 29^2 + 31^2.
%t LinearRecurrence[{5,-10,10,-5,1},{1,9,73,289,801},40] (* _Harvey P. Dale_, Oct 22 2019 *)
%Y Cf. A001481.
%K nonn,easy
%O 0,2
%A _Lekraj Beedassy_, Jul 23 2004
%E Corrected and extended by _Ray Chandler_, Jul 29 2004
|
