A036319 -id:A036319 - cp's OEIS frontend

A020466 Primes that contain digits 4 and 9 only.

449, 499, 4999, 9949, 44449, 49499, 49999, 94949, 94999, 444449, 994949, 999499, 4444949, 4449449, 4944949, 4949449, 4999949, 4999999, 9444949, 9494999, 9944449, 9994499, 44444999, 44499449, 44944499, 44994949, 49444949, 49444999, 49494499

Offset: 1

David W. Wilson

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)

Cf. A036319 (composite numbers having all their prime factors in this sequence).

Flatten[Table[Select[FromDigits/@Tuples[{4,9},n],PrimeQ],{n,8}]] (* Vincenzo Librandi, Jul 27 2012 *)

is(N)=isprime(N)&&!#setminus(Set(digits(N)), [4,9]) \\ M. F. Hasler, Sep 22 2020

A036945 Smallest n-digit prime containing only the digits 4 and 9, or 0 if no such prime exists.

Original entry on oeis.org

0, 0, 449, 4999, 44449, 444449, 4444949, 44444999, 444499949, 4444444999, 44444449949, 444444494449, 4444449444949, 44444444449499, 444444444499499, 4444444444444999, 44444444444444999, 444444444449449949

Offset: 1

Patrick De Geest, Jan 04 1999

			44449 is the least prime of 5 digits containing just digits 4 and 9 so a(5) = 44449. - _David A. Corneth_, Oct 10 2019

David A. Corneth, Table of n, a(n) for n = 1..538

Cf. A036229, A020466, A036319, A036929-A036951.

Join[{0,0},Table[SelectFirst[10*FromDigits[#]+9&/@Tuples[{4,9},n],PrimeQ],{n,2,20}]] (* Harvey P. Dale, Aug 20 2021 *)

a(n) = my(s=4*(10^(n)-1)/9);forstep(i=1, 2^n-1, 2, fr = fromdigits(5 * binary(i)) + s; if(isprime(fr), return(fr))); 0 \\ David A. Corneth, Oct 10 2019

cp's OEIS Frontend

A020466 Primes that contain digits 4 and 9 only.

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