login
A236212
Floor of the value of Riemann's xi function at n.
1
0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 5, 8, 13, 21, 36, 63, 113, 206, 386, 736, 1433, 2849, 5773, 11919, 25059, 53613, 116658, 258032, 579856, 1323273, 3065246, 7204159, 17172291, 41498712, 101635485, 252180415, 633710357, 1612310803, 4151993262, 10819115820
OFFSET
1,9
COMMENTS
On the interval [1, infinity), the xi function takes real values and is (strictly) increasing, so a(n) <= a(n+1) for n >= 1.
Same as floor of the value of the xi function at 1-n, because of the functional equation xi(1-s) = x(s).
FORMULA
a(n) = [xi(n)] for n > 0.
EXAMPLE
xi(1) = 1/2, so a(1) = [0.5] = 0.
xi(8) = (4*Pi^4)/225 = 1.7317…, so a(8) = [1.7] = 1.
MATHEMATICA
xi[ s_] := If[ s == 1, 1/2, (s/2)*(s - 1)*Pi^(-s/2)*Gamma[ s/2]*Zeta[ s]]; Table[ Floor[ xi[ n]], {n, 40}]
CROSSREFS
Cf. A002410.
Sequence in context: A229194 A304790 A306486 * A293865 A337078 A024322
KEYWORD
nonn
AUTHOR
Jonathan Sondow, Jan 25 2014
STATUS
approved