OFFSET
1,2
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..168
MATHEMATICA
Table[ sum = 0; For[i = 1, i <= Prime[n] - 1 , i++, sum = sum*2;
If[! PrimeQ[i], sum++]]; IntegerString[sum, 2], {n, 1, 13}] (* Robert Price, Apr 03 2019 *)
PROG
(PARI) a(n) = fromdigits(vector(prime(n)-1, k, !isprime(k)), 10); \\ Michel Marcus, Apr 04 2019
(Python)
from sympy import isprime, prime
def a(n): return int("".join(str(1-isprime(i)) for i in range(1, prime(n))))
print([a(n) for n in range(1, 14)]) # Michael S. Branicky, Jan 10 2022
(Python) # faster version for initial segment of sequence
from sympy import isprime
from itertools import count, islice
def agen(): # generator of terms
an = 0
for k in count(1):
an = 10 * an + int(not isprime(k))
if isprime(k+1):
yield an
print(list(islice(agen(), 13))) # Michael S. Branicky, Jan 10 2022
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Omar E. Pol, Apr 08 2008
STATUS
approved