OFFSET
1,1
COMMENTS
Positive numbers k such that k^2 == 2 (mod 127).
LINKS
FORMULA
a(n) = (127-63*(-1)^(n-1)+254*(n-1))/4.
a(n) = a(n-1)+a(n-2)-a(n-3).
G.f.: x*(16+95*x+16*x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Aug 24 2011
Sum_{n>=1} (-1)^(n+1)/a(n) = cot(16*Pi/127)*Pi/127. - Amiram Eldar, Feb 28 2023
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {16, 111, 143}, 50] (* Harvey P. Dale, May 30 2014 *)
PROG
(Magma) [(127-63*(-1)^(n-1)+254*(n-1))/(4): n in [1..50]]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Dec 09 2010
STATUS
approved