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%I #7 Mar 08 2022 11:38:04
%S 11,3,32969,211725989
%N a(n) is the first start of a sequence of exactly n lower twin primes under the iteration p -> 3*p+2.
%C a(n), 3*a(n)+2, 9*(a(n)+1)-1, ..., 3^(n-1)*(a(n)+1)-1 are lower twin primes but 3^n*(a(n)+1)-1 is not.
%e a(3) = 32969 because 32969 and 32971 are primes, 3*32969+2 = 98909 and 98911 are primes, 3*98909+2 = 296729 and 296731 are primes, but 3*296729+2 = 890189 and 890191 are not both primes.
%Y Cf. A001359.
%K nonn,more
%O 1,1
%A _Robert Israel_, Mar 06 2022
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