A275649 Number of squarefree odd numbers k > 1 less than 10^n such that k is a sum of two squares.

2, 14, 112, 997, 8982, 82305, 764092, 7159654, 67581778, 641696858, 6122456540, 58649349611, 563729377405, 5434188304040, 52515178669973, 508607849995010

Offset: 1

Author

Felix Fröhlich, Aug 04 2016

Keywords

• nonn
• more

Comments

This sequence gives the values of the counting function U(x), whose values are given in table 2 on page 359 of Shiu, 1986.

Links

• P. Shiu, Counting sums of two squares: the Meissel-Lehmer method, Mathematics of Computation, 47 (1986), 351-360.

Crossrefs

Cf. A164775: W(x), A275650: V(x).

Programs

Mathematica

Table[Count[Range[1, 10^n, 2], k_ /; SquareFreeQ@ k && SquaresR[2, k] > 0], {n, 6}] (* Michael De Vlieger, Aug 04 2016 *)

Extensions

a(7), a(11) and a(12) corrected and a(13)-a(16) added by Hiroaki Yamanouchi, Dec 25 2016