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a(n) is the least x such that the n values x+0, x+6, x+12, ..., x+6*(n-1) are all products of exactly two primes (i.e., semiprimes).
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%I #10 Aug 06 2021 12:42:10

%S 4,4,9,203,1333,1333,1333,2159,8309,18799,60499,60499,186779,186779,

%T 186779,12015573923,12015573923,6763513182767

%N a(n) is the least x such that the n values x+0, x+6, x+12, ..., x+6*(n-1) are all products of exactly two primes (i.e., semiprimes).

%C a(19) > 1.e14 if it exists. - _Hugo van der Sanden_, Aug 06 2021

%e a(4)=203 because 203 = 7*29, 209 = 11*19, 215 = 5*43, 221 = 13*17.

%Y Cf. A082919, A092129. Row 6 of A124570.

%K nonn,fini

%O 1,1

%A _Don Reble_, Feb 25 2004

%E a(8) and a(9) corrected and a(18) from _Donovan Johnson_, Oct 01 2010