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

0,2

Links

Table of n, a(n) for n=0..104.

Formula

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

Equals A275647 - 1.

Example

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

Mathematica

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

Crossrefs

Cf. A002808, A275647.

Sequence in context: A154162 A046019 A021523 * A275647 A011436 A248317

Adjacent sequences: A335586 A335587 A335588 * A335590 A335591 A335592

Keyword

nonn,cons

Author

Jon E. Schoenfield, Jan 26 2021

Status

approved