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 A200677 Smallest semiprime such that the sum of the two prime divisors equals n, or zero if impossible. 0
 0, 0, 0, 4, 6, 9, 10, 15, 14, 21, 0, 35, 22, 33, 26, 39, 0, 65, 34, 51, 38, 57, 0, 95, 46, 69, 0, 115, 0, 161, 58, 87, 62, 93, 0, 155, 0, 217, 74, 111, 0, 185, 82, 123, 86, 129, 0, 215, 94, 141, 0, 235, 0, 329, 106, 159, 0, 265, 0, 371, 118, 177, 122, 183, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS For n > 3, a(n) = 0 if n-2 is composite. LINKS EXAMPLE a(10) = 21 because 21= 3*7 and 3+7 = 10. PROG with(numtheory):for n from 1 to 65 do:ii:=0:for k from 1 to 1000 while(ii=0)do:m1:=bigomega(k):x:=factorset(k): m2:=nops(x):if m1=2 and m2=2 and x[1]+x[2]= n or m1=2 and m2=1 and 2*x[1]= n then ii:=1: printf(`%d, `, k):else fi:od:if ii=0 then printf(`%d, `, 0):else fi:od: CROSSREFS Cf. A001358, A135093. Sequence in context: A142863 A132435 A108631 * A189553 A189482 A099303 Adjacent sequences:  A200674 A200675 A200676 * A200678 A200679 A200680 KEYWORD nonn AUTHOR Michel Lagneau, Nov 20 2011 STATUS approved

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