A157712 Smallest prime made up of 0's and prime(n) 1's (or 0 when no such prime exists).

11, 0, 101111, 11110111, 101111111111, 101101111111111, 101111111111111111, 1111111111111111111, 11111111111111111111111, 111110111111111111111111111111, 11111101111111111111111111111111

Offset

1,1

Comments

Smallest prime with digit sum A000040(n) and using only 0's and 1's. Subsequence of A157709.

Links

Chai Wah Wu, Table of n, a(n) for n = 1..168

Prog

(Python)
from __future__ import division
from itertools import combinations
from sympy import prime, isprime
def A157712(n):
    if n == 1:
        return 11
    if n == 2:
        return 0
    p = prime(n)
    l = p
    while True:
        for i in combinations(range(l), l-p):
            s = ['1']*l
            for x in i:
                s[x] = '0'
            q = int(''.join(s))
            if isprime(q):
                return q
        l += 1 # Chai Wah Wu, Nov 05 2015

Crossrefs

Cf. A054750.

Sequence in context: A073865 A036931 A165399 * A266379 A158215 A294254

Adjacent sequences: A157709 A157710 A157711 * A157713 A157714 A157715

Keyword

nonn,base

Author

Lekraj Beedassy, Mar 04 2009

Extensions

Extended by Ray Chandler, Mar 06 2009

Status

approved