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Search: id:A110606
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| A110606 |
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Numbers n whose base 8 representations, interpreted as base 10 integers, are semiprimes. |
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+0
7
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| 4, 6, 8, 12, 13, 17, 18, 21, 22, 27, 28, 29, 38, 41, 45, 47, 50, 53, 60, 63, 70, 73, 77, 81, 82, 83, 91, 92, 97, 98, 99, 101, 102, 109, 113, 118, 127, 129, 130, 131, 133, 134, 139, 140, 141, 143, 145, 150, 157, 159, 167, 171, 172, 178, 181, 183, 188, 193, 194, 195
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A108873 is the equivalent using base 3. A110602 is the equivalent using base 4. A110603 is the equivalent using base 5. A110604 is the equivalent using base 6. A110605 is the equivalent using base 7. A110607 is the equivalent using base 9.
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EXAMPLE
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a(1) = 4 because 4 (base 8) = 4 (base 10) = 2 * 2, a semiprime (A001358).
a(2) = 6 because 6 (base 8) = 6 (base 10) = 2 * 3.
a(3) = 8 because 8 (base 8) = 10, and 10 (base 10) = 2 * 5.
a(4) = 12 because 12 (base 8) = 14, and 14 (base 10) = 2 * 7.
a(5) = 13 because 13 (base 8) = 15, and 15 (base 10) = 3 * 5.
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MATHEMATICA
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Select[Range[195], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 8]]] == 2 &] (*Chandler*)
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CROSSREFS
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Cf. A001358, A007094, A108873, A110602, A110603, A110604, A110605, A110607.
Sequence in context: A014455 A110646 A031359 this_sequence A117247 A047407 A090697
Adjacent sequences: A110603 A110604 A110605 this_sequence A110607 A110608 A110609
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), Jul 30 2005
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 05 2005
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