A304856 Numbers k such that prime(k)^k - 2 is prime.

2, 4, 18, 19, 20, 21, 31, 38, 82, 94, 212

Offset

1,1

Comments

a(12) > 20000, if it exists. - Michael S. Branicky, Nov 30 2024

Links

Table of n, a(n) for n=1..11.

Example

2 is in the sequence because prime(2)^2 - 2 = 3^2 - 2 = 7.

Maple

N:=10000:
for X from 1 to N do
if isprime(ithprime(X)^X - 2) then print(X);
end if:
end do:

Mathematica

Select[Range[220], PrimeQ[Prime[#]^#-2]&] (* Harvey P. Dale, Apr 03 2019 *)

Prog

(PARI) select( is(n)=ispseudoprime(prime(n)^n-2), [1..222]) \\ M. F. Hasler, May 21 2018

Crossrefs

Cf. A303371.

Sequence in context: A242528 A137933 A143116 * A115987 A076692 A350629

Adjacent sequences: A304853 A304854 A304855 * A304857 A304858 A304859

Keyword

nonn,more

Author

David James Sycamore, May 19 2018

Status

approved