OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(10)=503, a prime, and 5! + 0! + 3! = 127, a prime.
MATHEMATICA
Select[Prime[Range[500]], PrimeQ[Total[IntegerDigits[#]!]]&] (* Harvey P. Dale, Mar 20 2016 *)
PROG
(PARI) {digitsumfac(n)=local(s, d); s=0; while(n>0, d=divrem(n, 10); n=d[1]; s=s+d[2]!); s}
{facp(m)=local(ct, sr); ct=0; sr=0; forprime(p=2, m, if(isprime(digitsumfac(p)), ct++; print1(p, " "); sr+=(1.0/p); )); print(); print("Found: "ct" primes < "m); print("Sum of reciprocals = "sr); }
(Python)
from sympy import isprime
from math import factorial
def f(n): return sum(factorial(int(d)) for d in str(n))
def ok(n): return isprime(n) and isprime(f(n))
print([k for k in range(3500) if ok(k)]) # Michael S. Branicky, Feb 11 2023
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jason Earls, Jun 24 2003
STATUS
approved