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 A245510 Records in A245509: smallest m > 1 such that the first odd number greater than m^k is prime for every 0 < k < n, but not for k = n. 5
 7, 5, 2, 105, 3, 909, 4995825, 28212939 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For more comments and a program, see A245509. a(9), if it exists, certainly exceeds 1050000000. It is not clear whether this sequence is infinite, nor whether a(n) is defined for every n. LINKS EXAMPLE a(4) = 105 because 105 is the smallest m such that the first odd numbers after m^k are prime for k = 1,2,3, but composite for k = 4. MATHEMATICA f[n_] := Block[{d = If[ OddQ@ n, 2, 1], m = 1, t}, While[t = n^m + d; EvenQ@ t || PrimeQ@ t, m++]; m]; t = Table[0, {25}]; k = 2; While[k < 29000000, a = f@ k; If[ t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++]; t (* Robert G. Wilson v, Aug 04 2014 *) PROG (PARI) a(n) = for(k=1, 10^6, c=0; for(i=1, n-1, if(isprime(k^i+(k%2)+1), c++)); if(c==n-1&&!isprime(k^n+(k%2)+1), return(k))) n=1; while(n<10, print1(a(n), ", "); n++) \\ Derek Orr, Jul 27 2014 CROSSREFS Cf. A245509, A245511, A245512, A245513, A245514. Sequence in context: A307160 A087273 A297879 * A199794 A106040 A320158 Adjacent sequences:  A245507 A245508 A245509 * A245511 A245512 A245513 KEYWORD nonn,hard,more AUTHOR Stanislav Sykora, Jul 24 2014 EXTENSIONS a(4) and example corrected by Derek Orr, Jul 27 2014 a(8) from Robert G. Wilson v, Aug 04 2014 STATUS approved

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Last modified October 19 16:17 EDT 2019. Contains 328223 sequences. (Running on oeis4.)