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 A309738 Primes of the form b^2*10^(2*k) + b*10^k + 1 for 1 <= b <= 9, k >= 0. 6
 3, 7, 13, 31, 43, 73, 421, 2551, 6481, 8191, 250501, 4002001, 64008001, 81009001, 40000200001, 90000300001, 64000008000001, 400000000020000000001, 3600000000060000000001, 64000000000008000000000001, 90000000000000300000000000001, 250000000000000500000000000001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE b | Primes of the form b^2*10^(2*k) + b*10^k + 1 --+------------------------------------------------------------- 1 | 3. 2 | 7, 421, 4002001, 40000200001, 400000000020000000001, ... 3 | 13, 90000300001, 90000000000000300000000000001, ... 4 | 5 | 31, 2551, 250501, 250000000000000500000000000001, ... 6 | 43, 3600000000060000000001, ... 7 | 8 | 73, 6481, 64008001, 64000008000001, ... 9 | 8191, 81009001, 810000000000000000900000000000000001, ... CROSSREFS Numbers k such that b^2*10^(2*k) + b*10^k + 1 are prime: A297422 (b=2), A306751 (b=3), A308449 (b=5), A309582 (b=6), A309719 (b=8), A309744 (b=9). Cf. A309739. Sequence in context: A342150 A002383 A163418 * A161218 A068679 A006978 Adjacent sequences:  A309735 A309736 A309737 * A309739 A309740 A309741 KEYWORD nonn,base AUTHOR Seiichi Manyama, Aug 15 2019 STATUS approved

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Last modified April 16 18:53 EDT 2021. Contains 343050 sequences. (Running on oeis4.)