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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. 3
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 11 23:44 EST 2019. Contains 329945 sequences. (Running on oeis4.)