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a(n) = least semiprime with factors not previously used containing integers 2n and 2n+1 as substrings.
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%I #10 Apr 13 2024 23:25:13

%S 1111,6,205,427,1577,11639,1651,22499,2771,34571,253411,5129,60491,

%T 59701,8149,9517,307793,122491,13579,53237,168019,18103,202451,21667,

%U 169963,377753,27613,301337,88391,34633,368413,750523,418573,44287

%N a(n) = least semiprime with factors not previously used containing integers 2n and 2n+1 as substrings.

%e Sequence:....1111....6...205...427...1577....11639....1651..

%e Factors.:..101*11..2*3..41*5..61*7..83*19..103*113..127*13..

%e 2n, 2n+1:.....0,1..2,3...4,5...6,7....8,9....10,11...12,13..

%e n ......:.......0....1.....2.....3......4........5.......6..

%K base,easy,nonn

%O 0,1

%A _Jason Earls_, Aug 22 2003

%E More terms from _Ray Chandler_, Aug 31 2003