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A124269
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3-almost primes indexed by primes.
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11
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12, 18, 27, 30, 50, 63, 75, 78, 102, 124, 130, 164, 172, 175, 190, 231, 246, 258, 279, 286, 292, 332, 345, 369, 404, 418, 425, 430, 435, 452, 524, 539, 574, 578, 606, 610, 638, 652, 663, 692, 722, 725, 775, 782, 795, 801, 854, 906, 916, 927, 938, 963, 969
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OFFSET
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1,1
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COMMENTS
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Primes indexed by 3-almostprimes = A124268. prime(3almostprime(n)) - 3almostprime(prime(n)) = A124270. See also A106349 Primes indexed by semiprimes. See also A106350 Semiprimes indexed by primes. See also A122824 Prime(semiprime(n)) - semiprime(prime(n)). Commutator [A000040,A001358] at n.
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 3almostprime(prime(1)) = 3almostprime(2) = 12 = 2^2 * 3.
a(2) = 3almostprime(prime(2)) = 3almostprime(3) = 18 = 2 * 3^2.
a(3) = 3almostprime(prime(3)) = 3almostprime(5) = 27 = 3^3.
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MAPLE
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A014612 := proc(n) option remember; if n = 1 then 8; else for a from procname(n-1)+1 do if numtheory[bigomega](a) = 3 then return a; end if; end do; end if; end proc:
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MATHEMATICA
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p3 = Select[Range[1000], PrimeOmega[#] == 3 &]; p3[[Prime@ Range@ PrimePi@ Length@ p3]] (* Giovanni Resta, Jun 13 2016 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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