A372491 Indices k such that A002533(k) is prime.

2, 3, 4, 5, 11, 17, 32, 53, 103, 107, 109, 113, 137, 197, 233, 811, 7993, 9281, 14387, 26573, 51361

Offset

1,1

Comments

All terms are either primes or powers of 2.

Links

Table of n, a(n) for n=1..21.

Formula

A111011(n) = A002533(a(n)).

Example

a(3) = 4 is a term because A002533(4) = 73 is prime.

Maple

B[0]:= 1: B[1]:= 1: R:= NULL: count:= 0:
for n from 2 while count < 18 do
  B[n]:= 2*B[n-1]+5*B[n-2];
  if (isprime(n) or n = 2^padic:-ordp(n, 2)) and isprime(A[n]) then
    R:= R, n; count:= count+1
  fi
od:
R;

Mathematica

Flatten[Position[LinearRecurrence[{2, 5}, {1, 1}, 1000] , _Integer?PrimeQ]-1] (* James C. McMahon, May 06 2024 *)

Crossrefs

Cf. A002533, A111011.

Sequence in context: A188532 A181288 A255260 * A333610 A052418 A051800

Adjacent sequences: A372488 A372489 A372490 * A372492 A372493 A372494

Keyword

nonn,more

Author

Robert Israel, May 03 2024

Extensions

a(21) from Michael S. Branicky, May 04 2024

Status

approved