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A114125
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a(n) = 10^n-th semiprime.
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5
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4, 26, 314, 3595, 40882, 459577, 5109839, 56168169, 611720495, 6609454805, 70937808071, 757060825018, 8040423200947, 85037651263063, 896113850117323
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MATHEMATICA
| fQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; c = 0; k = 2; Do[While[c < 10^n, If[fQ@k, c++ ]; k++ ]; Print[k - 1], {n, 0, 8}]
(* checked by *) SemiPrimePi[n_] := Sum[ PrimePi[n/Prime@i] - i + 1, {i, PrimePi@ Sqrt@n}]
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CROSSREFS
| Cf. A006880, A006988, A066265, A078972.
Sequence in context: A054592 A102202 A136503 * A063182 A194926 A167147
Adjacent sequences: A114122 A114123 A114124 * A114126 A114127 A114128
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 11 2006
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EXTENSIONS
| a(14) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 27 2010
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