OFFSET
1,1
REFERENCES
J. W. P. Hirschfeld, Linear codes and algebraic curves, pp. 35-53 of F. C. Holroyd and R. J. Wilson, editors, Geometrical Combinatorics. Pitman, Boston, 1984.
LINKS
Robin Visser, Table of n, a(n) for n = 1..1400
Jean-Pierre Serre, Sur le nombre des points rationnels d'une courbe algébrique sur un corps fini, C. R. Acad. Sci. Paris Ser. I Math. 296 (1983), no. 9, 397-402.
Gerard van der Geer et al., Tables of curves with many points
Gerard van der Geer and Marcel van der Vlugt, Tables of curves with many points, Math. Comp. 69 (2000) 797-810.
PROG
(Sage)
def a(n):
if (n%2 == 0): return 5^n + 1 + 4*5^(n/2)
elif ((floor(2*5^(n/2))%5 == 0) or (5^n-1).is_square()
or (4*5^n-3).is_square() or (4*5^n-7).is_square()):
if (frac(2*5^(n/2)) > ((sqrt(5)-1)/2)): return 5^n + 2*floor(2*5^(n/2))
else: return 5^n + 2*floor(2*5^(n/2)) - 1
else: return 5^n + 1 + 2*floor(2*5^(n/2)) # Robin Visser, Oct 01 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jul 05 2010
EXTENSIONS
More terms from Robin Visser, Oct 01 2023
STATUS
approved