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A178043 n-th semiprime minus number of distinct transpositions of digits (zeros and units) in n-th semiprime written in base 2. 1
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)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

a(n)=s-binomial((A000120(s)+A023416(s)), A000120(s)), where s=semiprime(n).

MATHEMATICA

#-Length[Permutations[IntegerDigits[#, 2]]]&/@Select[Range[ 2, 300], PrimeOmega[ #] == 2&] (* Harvey P. Dale, Jun 21 2014 *)

CROSSREFS

Cf. A001358, A122466.

Sequence in context: A202871 A144626 A033707 * A049925 A291873 A118114

Adjacent sequences:  A178040 A178041 A178042 * A178044 A178045 A178046

KEYWORD

nonn,base

AUTHOR

Juri-Stepan Gerasimov, May 17 2010

EXTENSIONS

More terms from R. J. Mathar, May 28 2010

STATUS

approved

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Last modified January 15 18:01 EST 2021. Contains 340188 sequences. (Running on oeis4.)