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 A199859 Numbers k such that 6k-5 is a composite number of the form (6x-5)*(6y-5) when x or y is not equal to 1 except for k=1. 2
 1, 9, 16, 23, 29, 30, 37, 42, 44, 51, 55, 58, 61, 65, 68, 72, 79, 80, 81, 86, 93, 94, 99, 100, 105, 107, 114, 118, 120, 121, 128, 130, 133, 135, 137, 142, 146, 149, 155, 156, 159, 161, 163, 170, 172, 175, 177, 180, 184, 185, 191, 192, 194, 198, 205, 211, 212 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Numbers whose associate in A091300 has at least one nontrivial factorization into two factors of A016921. LINKS MAPLE isA016921 := proc(n)     (n mod 6)=1 ; end proc: isA091300 := proc(n)     (not isprime(n)) and isA016921(n) ; end proc: isA199859 := proc(n)     if n = 1 then         return true;     elif isA091300(6*n-5) then         for d in numtheory[divisors](6*n-5) minus {1, 6*n-5} do             if isA016921(d) and isA016921((6*n-5)/d) then                 return true;             end if;         end do:         return false;     else         return false;     end if; end proc: for n from 1 to 210 do     if isA199859(n) then         printf("%d, ", n) ;     end if ; end do; # R. J. Mathar, Nov 25 2011 CROSSREFS Cf. A091300. Sequence in context: A045911 A287186 A134256 * A046463 A003332 A091571 Adjacent sequences:  A199856 A199857 A199858 * A199860 A199861 A199862 KEYWORD nonn,easy AUTHOR Eleonora Echeverri-Toro, Nov 11 2011 STATUS approved

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Last modified April 10 02:39 EDT 2020. Contains 333392 sequences. (Running on oeis4.)