A152447 Decimal expansion of the sum_q 1/(q*(q-1)) over the semiprimes q = A001358.

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

Offset

0,2

Comments

The semiprime analog of A136141. To obtain the (smaller) sum over the squarefree semiprimes A006881, subtract the prime zeta functions of 4 ( A085964 ), 6, 8 etc. from this constant here. The first term in the representation as the geometric series in powers 1/q^s is in A117543 .

Links

Table of n, a(n) for n=0..79.

R. J. Mathar, Series of reciprocal powers of k-almost primes, constant B_{2,1} in table 8.

Formula

Equals 0.17105189297999663662220256437237421399124661203550059749107997... = 1/(4*3)+1/(6*5)+1/(9*8)+1/(10*9)+...

Crossrefs

Sequence in context: A231096 A240907 A179376 * A198611 A298853 A351213

Adjacent sequences: A152444 A152445 A152446 * A152448 A152449 A152450

Keyword

cons,nonn

Author

R. J. Mathar, Dec 04 2008

Status

approved