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A117543 Decimal expansion of the sum of the reciprocals of squared semiprimes. 4
1, 4, 0, 7, 6, 0, 4, 3, 4, 3, 4, 9, 0, 2, 3, 3, 8, 8, 2, 2, 2, 7, 5, 0, 9, 2, 5, 4, 1, 3, 8, 7, 7, 2, 5, 3, 7, 7, 4, 9, 1, 9, 2, 7, 6, 0, 0, 4, 8, 8, 0, 2, 6, 3, 9, 2, 4, 1, 4, 8, 9, 7, 6, 8, 0, 7, 8, 9, 3, 8, 0, 2, 8, 0, 9, 7, 6, 0, 3, 5, 3, 8, 6, 9, 6, 3, 5, 0, 4, 4, 3, 4, 8, 6, 1, 3, 1, 3, 8, 2, 5, 7 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Geoffrey Landis and Jonathan Vos Post (personal communication) show that this constant equals ((P2)^2 + P4)/2, where P2 and P4 are constants in A085548 and A085964, respectively.

LINKS

Table of n, a(n) for n=0..101.

Richard J. Mathar, Series of Reciprocal Powers of k-almost Primes, Table 4.

Eric Weisstein's World of Mathematics, Math World: Prime Zeta Function

EXAMPLE

0.14076043434902338822275... = 1/4^2 + 1/6^2 + 1/9^2 + 1/10^2 + 1/14^2 +1/15^2 +...

CROSSREFS

Cf. A001358 (semiprimes), A154928 (derivative).

A131653 (squared triprimes) [From T. D. Noe, Oct 09 2008]

Sequence in context: A272876 A133930 A077892 * A242970 A070433 A169821

Adjacent sequences:  A117540 A117541 A117542 * A117544 A117545 A117546

KEYWORD

cons,nonn

AUTHOR

T. D. Noe, Mar 28 2006

STATUS

approved

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Last modified December 4 19:31 EST 2016. Contains 278755 sequences.