OFFSET
0,1
LINKS
Michael S. Branicky, Table of n, a(n) for n = 0..997 (terms 0..200 from M. F. Hasler)
PROG
(Python)
from sympy import isprime
def a(n):
if n < 2: return list([2, 5])[n]
n5s, i, pow10, end_digits = int('5'*n), 1, 1, 0
while True:
i = 1
while i < pow10:
istr = str(i)
if istr[0] == '5' and len(istr) == end_digits:
i += 2 if pow10 <= 10 else pow10 // 10
else:
t = n5s * pow10 + i
if isprime(t): return t
i += 2
pow10 *= 10; end_digits += 1
print([a(n) for n in range(20)]) # Michael S. Branicky, Feb 05 2021, corrected Mar 03 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Robert G. Wilson v, Nov 28 2001
EXTENSIONS
Corrected by N. J. A. Sloane, Jan 11 2007 and by Don Reble, Jan 17 2007
Offset corrected by Michael S. Branicky, Feb 05 2021
STATUS
approved