OFFSET
0,1
PROG
(Python)
from sympy import isprime
def f(w):
for s in w:
for t in range(int(s[-1])+1, 10, 2):
yield s+str(t)
def g(w):
for s in w:
for t in range(1-int(s[-1])%2, int(s[-1]), 2):
yield s+str(t)
def A343677(n):
if n == 0:
return 4
c = 0
for d in '1379':
x = d
for i in range(1, n+1):
x = g(x) if i % 2 else f(x)
c += sum(1 for p in x if isprime(int(p+p[-2::-1])))
y = d
for i in range(1, n+1):
y = f(y) if i % 2 else g(y)
c += sum(1 for p in y if isprime(int(p+p[-2::-1])))
return c
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Chai Wah Wu, Apr 25 2021
EXTENSIONS
a(17)-a(18) from Chai Wah Wu, May 02 2021
STATUS
approved