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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.
2
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
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
Sequence in context: A063909 A181575 A335070 * A194384 A287305 A189938
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Jun 06 2022
STATUS
approved