Numbers k such that (20^k+1)/21 is a prime.

A057186

Numbers k such that (20^k+1)/21 is a prime.

Terms

    a(0) =5a(1) =79a(2) =89a(3) =709a(4) =797a(5) =1163a(6) =6971a(7) =140053a(8) =177967a(9) =393257a(10) =463511

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