OFFSET
1,1
COMMENTS
Positive numbers k such that k^2 == 2 (mod 103).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
FORMULA
a(n) = (103+49*(-1)^(n-1)+206*(n-1))/4.
G.f.: x*(38+27*x+38*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Aug 24 2011
Sum_{n>=1} (-1)^(n+1)/a(n) = tan(27*Pi/206)*Pi/103. - Amiram Eldar, Feb 28 2023
MATHEMATICA
CoefficientList[Series[(38 + 27 x + 38 x^2)/((1 + x) (x - 1)^2), {x, 0, 50}], x] (* Vincenzo Librandi, Sep 24 2014 *)
LinearRecurrence[{1, 1, -1}, {38, 65, 141}, 50] (* Harvey P. Dale, Nov 21 2021 *)
PROG
(Magma) [(103+49*(-1)^(n-1)+206*(n-1))/(4): n in [1..50]];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Dec 09 2010
STATUS
approved