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A122466
Semiprimes written in base 2.
3
100, 110, 1001, 1010, 1110, 1111, 10101, 10110, 11001, 11010, 100001, 100010, 100011, 100110, 100111, 101110, 110001, 110011, 110111, 111001, 111010, 111110, 1000001, 1000101, 1001010, 1001101, 1010010, 1010101, 1010110, 1010111, 1011011, 1011101, 1011110, 1011111
OFFSET
1,1
COMMENTS
Semiprime analog of A004676 Primes written in base 2. Partial sums are A122467; equivalently, this sequence is the first differences of A122467.
FORMULA
a(n) = A007088(A001358(n)).
MATHEMATICA
lim=100; SP=Select[Range[lim], PrimeOmega[#]==2&]; ll=Length[SP]; Table[FromDigits[IntegerDigits[SP[[n]], 2]], {n, ll}] (* James C. McMahon, Oct 27 2024 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, Sep 09 2006
EXTENSIONS
a(31)-a(34) from James C. McMahon, Oct 27 2024
STATUS
approved