A354748 a(n) is the prime reached after A354747(n) steps when repeatedly applying the map x -> 3*x+2 to 2*n-1, or 0 if no prime is ever reached.

5, 11, 17, 23, 29, 107, 41, 47, 53, 59, 197, 71, 233, 83, 89, 863, 101, 107, 113, 359, 2480057, 131, 137, 431, 149, 467, 4373, 167, 173, 179, 557, 191, 197, 5507, 1889, 647, 1997, 227, 233, 239, 2213, 251, 257, 263, 269, 827, 281, 863, 293, 2699, 2753, 311, 317

Offset

1,1

Comments

Is a(100943) = 0?

If not 0, a(100943) >= 10^10000. - Michael S. Branicky, Jun 07 2022

Links

Table of n, a(n) for n=1..53.

Prog

(PARI) a(n) = my(x=2*n-1); while(1, x=3*x+2; if(ispseudoprime(x), return(x)))
(Python)
from sympy import isprime
def f(x): return 3*x + 2
def a(n):
    fn, c = f(2*n-1), 1
    while not isprime(fn): fn, c = f(fn), c+1
    return fn
print([a(n) for n in range(1, 54)]) # Michael S. Branicky, Jun 07 2022

Crossrefs

Cf. A052333, A354747.

Sequence in context: A063909 A181575 A335070 * A194384 A287305 A189938

Adjacent sequences: A354745 A354746 A354747 * A354749 A354750 A354751

Keyword

nonn

Author

Felix Fröhlich, Jun 06 2022

Status

approved