A089150 a(1) = 1; for > 1, a(n) = smallest m such that n^m - {(n-1)^a(n-1)} is a positive prime.

1, 2, 2, 2, 3, 4, 5, 13, 28, 31, 37, 58, 89, 747, 1252

Offset

1,2

Comments

a(16) does not exist because 16^k - 15^1252 = (4^k - 15^626) * (4^k + 15^626) can't be a prime. - Robert Israel, Dec 23 2024

Links

Table of n, a(n) for n=1..15.

Maple

A[1]:= 1:
for n from 2 to 15 do
  t:= (n-1)^A[n-1];
  for k from ceil(log[n](t)) do
    if isprime(n^k - t) then A[n]:= k; break fi
  od;
od:
seq(A[i], i=1..15); # Robert Israel, Dec 23 2024

Mathematica

k = 1; Do[m = 1; While[n^m < (n-1)^k || !PrimeQ[n^m - (n-1)^k], m++ ]; k = m; Print[k], {n, 2, 15}] (* Ryan Propper, Jul 15 2005 *)

Crossrefs

Cf. A089149.

Sequence in context: A357384 A022865 A373785 * A056697 A132427 A176975

Adjacent sequences: A089147 A089148 A089149 * A089151 A089152 A089153

Keyword

nonn,fini,full

Author

Naohiro Nomoto, Dec 06 2003

Extensions

Two more terms from Ryan Propper, Jul 15 2005

Status

approved