

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




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

Table of n, a(n) for n=1..8.


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, n1, if(isprime(k^i+(k%2)+1), c++)); if(c==n1&&!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: A021934 A021097 A087273 * A199794 A106040 A085927
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



