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A337768
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Decimal expansion of the sum of reciprocals of squared composite numbers that are not prime powers.
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1
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0, 9, 3, 2, 4, 0, 7, 6, 9, 1, 9, 1, 2, 2, 7, 2, 5, 2, 0, 3, 2, 6, 8, 4, 1, 4, 2, 6, 7, 4, 6, 8, 1, 6, 1, 1, 0, 8, 7, 4, 4, 9, 5, 2, 3, 4, 2, 8, 1, 7, 0, 1, 8, 5, 5, 0, 4, 9, 4, 0, 8, 9, 5, 3, 1, 0, 4, 4, 1, 8, 7, 2, 7, 6, 2, 1, 3, 0, 2, 0, 2, 7, 5, 5, 8, 7, 7, 9
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OFFSET
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0,2
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LINKS
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FORMULA
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Equals Sum_{k>=1} (1/(A024619(k)^2).
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EXAMPLE
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Equals 1/(6^2) + 1/(10^2) + 1/(12^2) + 1/(14^2) + ... + = 0.0932407691912272520326841426746816110874495234281701855...
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MATHEMATICA
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A337768[n_] := 1/Select[Range[n, n], ! PrimePowerQ[#] && CompositeQ[#] &] N[Total[ParallelTable[A337768[k]^2, {k, 2, 10^8}]/.{} -> Sequence[]], 62]
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PROG
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(Sage)
sum_A337768 = (i for i in NN if i>3 and not i.is_prime() and not i.is_prime_power())
s = RLF(0); s
RealField(110)(s)
for i in range(0, 5000000): s += 1 / next(sum_A337768)^2
print(s) #
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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