A364453 Smallest k such that 5^(5^n) - k is prime.

4, 64, 124, 228, 10978, 73738

Offset

1,1

Comments

This is to 5 as A058220 is to 2 and A140331 is to 3.

a(7) > 5487.

Links

Table of n, a(n) for n=1..6.

Formula

a(n) = A064722(A137841(n)).

Example

a(2) = 64 because 5^(5^2) - 64 = 298023223876953061 is prime.

Mathematica

lst={}; Do[Do[p=5^(5^n)-k; If[PrimeQ[p], AppendTo[lst, k]; Break[]], {k, 2, 11!}], {n, 7}]; lst
Table[k=1; Monitor[Parallelize[While[True, If[PrimeQ[5^(5^n)-k], Break[]]; k++]; k], k], {n, 1, 7}]
y[n_] := Module[{x = 5^(5^n)}, x - NextPrime[x, -1]]; Array[y, 7]

Prog

(PARI) a(n) = my(x = 5^(5^n)); x - precprime(x);

Crossrefs

Cf. A064722, A137841.

Cf. A058220, A140331, A364452, A364454.

Sequence in context: A367913 A210935 A090561 * A273375 A016934 A260182

Adjacent sequences: A364450 A364451 A364452 * A364454 A364455 A364456

Keyword

more,nonn

Author

J.W.L. (Jan) Eerland, Jul 25 2023

Status

approved