OFFSET
1,3
COMMENTS
a(n) = n-1 iff a(n) is in A035346 for n > 1.
LINKS
Michel Marcus, Table of n, a(n) for n = 1..1000
FORMULA
a(n) < n.
PROG
(PARI) a(n) = {my(k=1); while(k, if(ispseudoprime(prod(i=1, n-k, prime(i)) + prime(n)), return(n-k)); k++)}
(Python)
from itertools import count
from sympy import isprime, prime, primorial
def A002110(n): return primorial(n) if n > 0 else 1
def A265109(n):
pn = prime(n)
return next(k for k in range(n-1, -1, -1) if isprime(pn+A002110(k)))
print([A265109(n) for n in range(1, 31)]) # Michael S. Branicky, Jan 10 2025
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Dec 01 2015
STATUS
approved