A157712 - OEIS

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

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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