A335589 Decimal expansion of the sum of the reciprocals of the squares of composite numbers.

1, 9, 2, 6, 8, 6, 6, 4, 6, 8, 0, 7, 1, 6, 0, 9, 3, 7, 9, 6, 5, 8, 7, 1, 8, 0, 1, 8, 1, 3, 7, 7, 7, 2, 5, 5, 0, 4, 5, 7, 1, 8, 5, 5, 7, 9, 6, 6, 9, 0, 6, 0, 1, 5, 9, 9, 9, 1, 3, 9, 2, 9, 9, 0, 1, 8, 8, 4, 2, 4, 4, 3, 0, 3, 9, 2, 8, 9, 9, 9, 9, 3, 8, 4, 6, 7, 1, 3, 5, 6, 2, 6, 4, 8, 5, 1, 8, 4, 7, 0, 8, 1, 1, 9, 8

Offset: 0

Author

Jon E. Schoenfield, Jan 26 2021

Keywords

• nonn
• cons

Examples

			Equals 1/4^2 + 1/6^2 + 1/8^2 + 1/9^2 + 1/10^2 + ... = 0.19268664680716093796587180181377725504571855796690...
		

Crossrefs

Cf. A002808, A275647.

Programs

Mathematica

First[RealDigits[Zeta[2] - PrimeZetaP[2] - 1, 10, 100]] (* Paolo Xausa, Feb 27 2025 *)

Formula

Equals Sum_{k>=1} 1/A002808(k)^2.

Equals A275647 - 1.