Pi/10 - sqrt((5 - sqrt(5))/32).
2, 0, 2, 6, 6, 6, 3, 9, 2, 1, 2, 7, 4, 2, 7, 5, 9, 2, 6, 1, 9, 1, 1, 3, 6, 1, 0, 0, 8, 4, 1, 3, 9, 0, 4, 1, 2, 0, 8, 9, 0, 7, 2, 1, 1, 1, 5, 9, 3, 7, 5, 8, 6, 5, 6, 1, 3, 5, 8, 2, 1, 8, 8, 5, 2, 1, 4, 2, 4, 0, 3, 5, 4, 7, 4, 4, 4, 9, 2, 1, 1, 0, 8, 5, 5, 1, 4, 5, 7, 6, 0, 2, 8, 4, 1, 0, 3, 8, 8, 1, 8, 1, 8, 8, 2
-1
When an 10-gon is inscibed in a unit circle, this is the area of one of the ten segments of the circle not in the 10-gon.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
Eric W. Weisstein, Circular segment
Wikipedia, Circular segment
This is Pi/n - sqrt((p^2+q^2)*((p-1)^2+q^2)), where p = (1 + cos(2*Pi/n))/2 and q = sin(2*Pi/n)/2 for n=10.
The number is 0.0202666392127427592619113610084139041208907211159….
(Mma) RealDigits[Pi/10 - Sqrt[(5 - Sqrt[5])/32], 10, 105][[1]]
Cf. S000236, S000237, S000238, S000243-S000249, S000250, S000251.
nonn,cons
T. D. Noe, Sep 05 2014