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A178043
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n-th semiprime minus number of distinct transpositions of digits (zeros and units) in n-th semiprime written in base 2.
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1
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1, 3, 3, 4, 10, 14, 11, 12, 15, 16, 18, 19, 15, 18, 24, 31, 29, 36, 49, 42, 43, 56, 44, 34, 39, 42, 47, 50, 51, 66, 70, 72, 73, 88, 71, 104, 94, 97, 112, 100, 101, 116, 101, 77, 78, 71, 72, 87, 89, 90, 99, 102, 131, 105, 96, 99, 107, 108, 155, 129, 159, 138, 131, 132, 147
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n)=s-binomial((A000120(s)+A023416(s)), A000120(s)), where s=semiprime(n).
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MATHEMATICA
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#-Length[Permutations[IntegerDigits[#, 2]]]&/@Select[Range[ 2, 300], PrimeOmega[ #] == 2&] (* Harvey P. Dale, Jun 21 2014 *)
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CROSSREFS
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Cf. A001358, A122466.
Sequence in context: A202871 A144626 A033707 * A049925 A291873 A118114
Adjacent sequences: A178040 A178041 A178042 * A178044 A178045 A178046
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KEYWORD
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nonn,base
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AUTHOR
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Juri-Stepan Gerasimov, May 17 2010
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EXTENSIONS
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More terms from R. J. Mathar, May 28 2010
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STATUS
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approved
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