OFFSET
1,1
COMMENTS
Denominator of circle radius r(n) is A143025(n+2). The integral radius appearing at n = 2, 6, 10, 14, ..., = 1, 5, 13, 25, ..., respectively which is A001844(n/4 - 1/2). Floor (r(n)) = A001971(n). For the case of sagitta = n and chord length = 1, the numerator and the denominator will be A053755(n) and A008590(n) respectively. See illustration in links.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Kival Ngaokrajang, Illustration for n = 1..5
Wikipedia, Sagitta
FORMULA
a(n) = numerator(n^2/8 + 1/2).
Empirical g.f.: -x*(x^11 +5*x^10 +x^9 +13*x^8 +2*x^7 +14*x^6 +2*x^5 +14*x^4 +5*x^3 +13*x^2 +x +5) / ((x -1)^3*(x +1)^3*(x^2 +1)^3). - Colin Barker, Jan 17 2015
PROG
(PARI){for (n=1, 100, print1(numerator(n^2/8+1/2), ", "))}
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Kival Ngaokrajang, Jun 13 2014
STATUS
approved