A090537 Least n-digit prime using digit 3 once and rest all 1, or 0 if no such prime exists.

3, 13, 113, 0, 11113, 113111, 0, 11111131, 111111113, 0, 11111111113, 111113111111, 0, 31111111111111, 0, 0, 11111111113111111, 111111111111111131, 0, 11111111111111111131, 131111111111111111111, 0, 11111111111111111311111

Offset

1,1

Links

Table of n, a(n) for n=1..23.

Formula

a(3n+1) = 0.

Prog

(Python)
from sympy import isprime
def agen():
  digits = 0
  while True:
    for i in range(digits+1):
      t = int("1"*(digits-i) + "3" + "1"*i)
      if isprime(t): yield t; break
    else: yield 0
    digits += 1
g = agen()
print([next(g) for i in range(23)]) # Michael S. Branicky, Mar 13 2021

Crossrefs

Cf. A090535, A090536, A090538.

Without zeros, subsequence of A107689.

Sequence in context: A223911 A006860 A181083 * A063269 A105431 A360187

Adjacent sequences: A090534 A090535 A090536 * A090538 A090539 A090540

Keyword

base,nonn

Author

Amarnath Murthy, Dec 08 2003

Extensions

More terms from David Wasserman, Jan 03 2006

Status

approved