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

Author

Felix Fröhlich, Jun 06 2022

Keywords

• nonn

Comments

Is a(100943) = 0?

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

Crossrefs

Cf. A052333, A354747.

Programs

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