OFFSET
1,2
COMMENTS
Nonprime numbers of the form k*10+1. - Juri-Stepan Gerasimov, Oct 14 2009
EXAMPLE
a(4) = 91 may look prime to some, but is composite.
MAPLE
remove(isprime, [10*j+1$j=0..99])[]; # Alois P. Heinz, Jan 21 2021
PROG
(PARI) isok(n) = ((n % 10) == 1) && (! isprime(n)) \\ Michel Marcus, Jul 26 2013
(Python)
from sympy import isprime
def aupto(lim): return [m for m in range(1, lim+1, 10) if not isprime(m)]
print(aupto(871)) # Michael S. Branicky, Jan 21 2021
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Enoch Haga, Feb 29 2000
STATUS
approved