OFFSET
1,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..16812 (first 1000 terms from Seiichi Manyama)
EXAMPLE
From Seiichi Manyama, Mar 24 2018: (Start)
n | a(n) |
--+------+------------------
1 | 2 | 2!
2 | 3 | 2! + 1!
3 | 7 | 3! + 1!
4 | 31 | 4! + 3! + 1!
5 | 127 | 5! + 3! + 1!
6 | 151 | 5! + 4! + 3! + 1! (End)
PROG
(Python)
from sympy import isprime
def facbase(k, f):
return sum(f[i] for i, bi in enumerate(bin(k)[2:][::-1]) if bi == "1")
def auptoN(N): # terms up to N factorial-base digits; 20 generates b-file
f = [factorial(i) for i in range(1, N+1)]
return list(filter(isprime, (facbase(k, f) for k in range(2**N))))
print(auptoN(10)) # Michael S. Branicky, Oct 15 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Nov 07 2003
EXTENSIONS
More terms from Vladeta Jovovic, Nov 08 2003
STATUS
approved