OFFSET
1,1
LINKS
Jon E. Schoenfield, Table of n, a(n) for n = 1..10000 (first 1001 terms from Harvey P. Dale)
EXAMPLE
k=156 is a term because the largest prime < 156 is 151 and '156151' is a prime.
MATHEMATICA
Select[Range[250], PrimeQ[FromDigits[Join[IntegerDigits[#], IntegerDigits[ NextPrime[ #, -1]]]]]&] (* Harvey P. Dale, Jul 10 2017 *)
PROG
(Python)
from sympy import isprime, prevprime
def ok(n): return isprime(int(str(n) + str(prevprime(n))))
print(list(filter(ok, range(3, 215)))) # Michael S. Branicky, Apr 05 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Oct 15 1998
STATUS
approved