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%I #10 Jun 17 2017 03:49:29
%S 1,21,73,157,273,421,601,813,1057,1333,1641,1981,2353,2757,3193,3661,
%T 4161,4693,5257,5853,6481,7141,7833,8557,9313,10101,10921,11773,12657,
%U 13573,14521,15501,16513,17557,18633,19741,20881,22053,23257,24493
%N 16n^2+4n+1.
%C 5th row of A082039 Case k=4 of family T(n,k)=k^2n^2+kn+1.
%C Also sequence found by reading the segment (1, 21) together with the line from 21, in the direction 21, 73,..., in the square spiral whose vertices are the generalized decagonal numbers A074377. - _Omar E. Pol_, Nov 02 2012
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F G.f.: ( -1-18*x-13*x^2 ) / (x-1)^3 . - _R. J. Mathar_, Dec 03 2014
%o (PARI) a(n)=16*n^2+4*n+1 \\ _Charles R Greathouse IV_, Jun 17 2017
%Y Cf. A082040, A054569.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Apr 02 2003
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