A020452 Primes that contain digits 1 and 4 only.

11, 41, 4111, 4441, 11411, 14411, 41141, 41411, 44111, 1114111, 1144141, 1144441, 1411141, 1411411, 1441411, 1444111, 1444411, 1444441, 4141441, 4414411, 4441111, 4441441, 11111141, 11141111, 11141441, 11441141, 11441411, 14111441, 14141411

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..20000 (first 1000 terms from Vincenzo Librandi)
• James Maynard and Brady Haran, Primes without a 7, Numberphile video (2019).

Crossrefs

Cf. A032822.

Programs

Magma

[p: p in PrimesUpTo(14141411) | Set(Intseq(p)) subset [1,4]]; // Bruno Berselli, Jul 27 2012

Mathematica

Flatten[Table[Select[FromDigits/@Tuples[{1,4},n],PrimeQ],{n,8}]] (* Vincenzo Librandi, Jul 27 2012 *)

Python

from sympy import primerange
def checkd(a, c):
    b =  set(int(i) for i in set(str(a)))
    return b.issubset(c)
for n in primerange(2, 2000000):
    if checkd(n, [1, 4]):
        print(n)
# Abhiram R Devesh, May 08 2015