A364452 - OEIS

A364452

Smallest k such that 4^(4^n) - k is prime.

5, 5, 159, 569, 1557, 2439, 25353, 24317, 164073

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OFFSET

1,1

COMMENTS

This is to 4 as A058220 is to 2 and A140331 is to 3.

a(8) > 22174.

LINKS

FORMULA

a(n) = A058220(2*n+1). - Michael S. Branicky, Aug 23 2024

EXAMPLE

a(2) = 5 because 4^(4^2) - 5 = 4294967291 is prime.

MATHEMATICA

lst={}; Do[Do[p=4^(4^n)-k; If[PrimeQ[p], AppendTo[lst, k]; Break[]], {k, 2, 11!}], {n, 7}]; lst

Table[k=1; Monitor[Parallelize[While[True, If[PrimeQ[4^(4^n)-k], Break[]]; k++]; k], k], {n, 1, 7}]

y[n_] := Module[{x = 4^(4^n)}, x - NextPrime[x, -1]]; Array[y, 7]

PROG

(PARI) a(n) = my(x = 4^(4^n)); x - precprime(x);

CROSSREFS

KEYWORD

more,nonn

AUTHOR

EXTENSIONS

a(8) using search and a(9) using A058220 from Michael S. Branicky, Aug 23 2024

STATUS

approved