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Search: id:A117881
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| A117881 |
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First semiprime after pi^n. |
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+0
1
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| 4, 4, 10, 33, 106, 309, 965, 3022, 9489, 29813, 93649, 294209, 924271, 2903678, 9122173, 28658147, 90032221, 282844574, 888582413, 2791563955, 8769956797, 27551631845, 86556004193, 271923706897, 854273519921, 2683779414319
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Pi and semiprime analogue of A074496 First prime after e^n. Lim [n approaches infinity] a(n+1)/a(n) = pi. See also A000796 Decimal expansion of Pi. There are numbers where floor(pi^n) is itself a semiprime, as with floor(pi^2) = 9, floor(pi^6) = 961 = 31^2, floor(pi^9) = 29809 = 13 * 2293, floor(pi^25) = 2683779414317 = 5749 * 466825433.
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LINKS
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Eric Weisstein's World of Mathematics, e-Prime.
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FORMULA
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a(n) = min{s in A001358 and s > pi^n}.
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EXAMPLE
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a(3) = 33 because pi^3 = 31.0062766... floor(pi^3) = 31 is prime hence 31 + 2 = 33 is a term.
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CROSSREFS
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Cf. A000040, A000149, A000796, A001358, A007512, A014210, A050808, A050809, A059303, A064118, A095935, A115019, A074496, A118840.
Sequence in context: A087288 A095009 A145598 this_sequence A006343 A107856 A128499
Adjacent sequences: A117878 A117879 A117880 this_sequence A117882 A117883 A117884
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), May 02 2006
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