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 A200927 Difference between (least semiprime >= n) and (largest semiprime <= n). 1
 0, 2, 0, 3, 3, 0, 0, 4, 4, 4, 0, 0, 6, 6, 6, 6, 6, 0, 0, 3, 3, 0, 0, 7, 7, 7, 7, 7, 7, 0, 0, 0, 3, 3, 0, 0, 7, 7, 7, 7, 7, 7, 0, 3, 3, 0, 2, 0, 4, 4, 4, 0, 2, 0, 0, 4, 4, 4, 0, 3, 3, 0, 4, 4, 4, 0, 5, 5, 5, 5, 0, 3, 3, 0, 5, 5, 5, 5, 0, 3, 3, 0, 0, 0, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,2 COMMENTS a(n) = 0 if and only if n is semiprime. LINKS Arkadiusz Wesolowski, Table of n, a(n) for n = 4..10000 MAPLE A106325 := proc(n) for a from n do if numtheory[bigomega](a) = 2 then return a; end if; end do: end proc; prevSpr := proc(n) for a from n by -1 do if numtheory[bigomega](a) = 2 then return a; end if; end do: end proc; A200927 := proc(n) A106325(n)-prevSpr(n) ; end proc: seq(A200927(n), n=4..80) ; # R. J. Mathar, Nov 26 2011 MATHEMATICA Table[a = b = 0; While[! PrimeOmega[n - a] == 2, a++]; While[! PrimeOmega[n + b] == 2, b++]; a + b, {n, 4, 100}] CROSSREFS Cf. A001358, A065516. Sequence in context: A219187 A049799 A087985 * A372820 A372819 A372818 Adjacent sequences: A200924 A200925 A200926 * A200928 A200929 A200930 KEYWORD nonn AUTHOR Arkadiusz Wesolowski, Nov 24 2011 STATUS approved

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Last modified September 8 17:50 EDT 2024. Contains 375753 sequences. (Running on oeis4.)