%I #30 Feb 26 2023 02:33:27
%S 22,59,103,140,184,221,265,302,346,383,427,464,508,545,589,626,670,
%T 707,751,788,832,869,913,950,994,1031,1075,1112,1156,1193,1237,1274,
%U 1318,1355,1399,1436,1480,1517,1561,1598,1642,1679,1723,1760,1804,1841,1885
%N Numbers k such that k^2 + 2 == 0 (mod (9^2)).
%C Numbers k such that k mod 81 is 22 or 59. - _Charles R Greathouse IV_, Dec 23 2011
%H Vincenzo Librandi, <a href="/A156797/b156797.txt">Table of n, a(n) for n = 1..1000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F Sum_{n>=1} (-1)^(n+1)/a(n) = tan(37*Pi/162)*Pi/81. - _Amiram Eldar_, Feb 26 2023
%t Select[Range[2000],PowerMod[#,2,81]==79&] (* _Harvey P. Dale_, Jun 30 2011 *)
%t LinearRecurrence[{1,1,-1},{22,59,103},50] (* _Vincenzo Librandi_, Feb 09 2012 *)
%o (PARI) a(n)=n\2*81-22*(-1)^n \\ _Charles R Greathouse IV_, Dec 23 2011
%o (Magma) I:=[22, 59, 103]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..50]]; // _Vincenzo Librandi_, Feb 09 2012
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Feb 16 2009