A090873 a(n) is the smallest number m such that n^2^k + m^2^k is prime for k=0,1,2,3 and 4.

1, 1, 218368, 9324385, 6628674, 601, 365082, 532253, 449140, 4193407, 175746, 2857547, 2752708, 6315245, 80612, 3354745, 10892, 953, 6577504, 157437, 2247676, 11357637, 7650, 272935, 318784, 8034141, 1158380, 22315, 610550, 340357

Offset

1,3

Links

Table of n, a(n) for n=1..30.

Formula

a[n_] := (For[m=1, !(PrimeQ[m+n]&&PrimeQ[m^2+n^2]&&PrimeQ[m^4+n^4]&& PrimeQ[m^8+n^8]&&PrimeQ[m^16+n^16]), m++ ];m)

Example

a(2)=1 because 2^2^k + 1 is prime for k= 0,1,2,3 and 4.

Mathematica

a[n_] := (For[m=1, !(PrimeQ[m+n]&&PrimeQ[m^2+n^2]&&PrimeQ[m^4+n^4]&& PrimeQ[m^8+n^8]&&PrimeQ[m^16+n^16]), m++ ]; m); Do[Print[a[n]], {n, 50}]

Crossrefs

Cf. A090872, A019434, A000215.

Sequence in context: A205915 A205907 A157377 * A236040 A251480 A072189

Adjacent sequences: A090870 A090871 A090872 * A090874 A090875 A090876

Keyword

nonn

Author

Farideh Firoozbakht, Feb 06 2004

Status

approved