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A175664
Greater of twin semiprimes.
2
10, 14, 25, 26, 38, 39, 55, 62, 69, 86, 91, 95, 115, 119, 122, 123, 133, 145, 146, 159, 187, 205, 206, 209, 213, 217, 218, 219, 221, 253, 278, 291, 295, 299, 302, 303, 305, 309, 323, 327, 339, 362, 365, 381, 386, 395, 398, 407, 411, 415, 417, 451, 458, 473
OFFSET
1,1
COMMENTS
Semiprimes m such that m-4 is also semiprime.
LINKS
FORMULA
a(n) = 4 + A175648(n). - R. J. Mathar, Aug 07 2010
EXAMPLE
a(1)=10 because 10 (semiprime) - 4 = 6 (semiprime);
a(2)=14 because 14 (semiprime) - 4 = 10 (semiprime).
MAPLE
A175664 := proc(n) option remember; if n = 1 then 10; else for a from procname(n-1)+1 do if numtheory[bigomega](a) = 2 and numtheory[bigomega](a-4) = 2 then return a; end if; end do: end if; end proc: seq(A175664(n), n=1..100) ; # R. J. Mathar, Aug 07 2010
MATHEMATICA
SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 500}], {1, _, _, _, 1}][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 16 2017 *)
CROSSREFS
Cf. A006512 (greater of twin primes), A175612 (list of twin semiprimes), A175648 (lesser of twin semiprimes).
Sequence in context: A168671 A136197 A071620 * A053690 A177948 A176140
KEYWORD
nonn
AUTHOR
EXTENSIONS
Corrected (313 removed) by R. J. Mathar, Aug 07 2010
STATUS
approved