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%I #72 Mar 07 2023 11:01:14
%S 19,37,53,67,79,89,97,103,107,109,109,107,103,97,89,79,67,53,37,19,-1,
%T -23,-47,-73,-101,-131,-163,-197,-233,-271,-311,-353,-397,-443,-491,
%U -541,-593,-647,-703,-761,-821,-883,-947,-1013,-1081,-1151,-1223,-1297,-1373,-1451,-1531,-1613
%N a(n) = -n^2 + 21*n - 1.
%C All the positive numbers of the form -(x^2 - 21*x + 1) are primes. Compare A335984.
%D T. Özsoy, Visualization of Prime Numbers: Twin Prime Numbers, Ozsoy Triangle and Ozsoy Series, in A. Baki, B. Güven, and M. Güler, editors, Proc. 4th International Symposium of Turkish Computer and Mathematics Education, 26-Sep 28 2019, İzmir; pages 678-688.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F G.f.: (x^2 + 20*x - 19)/(x - 1)^3. - _Jinyuan Wang_, Jul 08 2020
%t Table[-n^2+21n-1,{n,60}] (* or *) LinearRecurrence[{3,-3,1},{19,37,53},60] (* _Harvey P. Dale_, Mar 07 2023 *)
%o (PARI) a(n)=-n^2+21*n-1 \\ _Charles R Greathouse IV_, Oct 21 2022
%Y Cf. A059425, A335984.
%K sign,easy
%O 1,1
%A _Tamer Özsoy_, Jul 02 2020
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