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%I #31 Sep 08 2022 08:44:45
%S 2,11,211,2111,2221,12211,21121,21211,21221,22111,111121,111211,
%T 112111,112121,1111211,1121221,1212121,1212221,1221221,2121121,
%U 2211211,2221111,11221211,12111221,12121121,12121211,12122111,12122221,12212111,12222121
%N Primes that contain digits 1 and 2 only.
%H Vincenzo Librandi, <a href="/A020450/b020450.txt">Table of n, a(n) for n = 1..1000</a>
%t Flatten[Table[Select[FromDigits/@Tuples[{1,2},n],PrimeQ],{n,8}]] (* _Vincenzo Librandi_, Jul 28 2012 *)
%o (PARI) for(nd=1,9, forvec(v=vector(nd,i,[49,50-(i==nd && i>1)]), isprime(t=eval(Strchr(Vecsmall(v)))) && print1(t","))) \\ _M. F. Hasler_, Mar 18 2010
%o (Magma) [p: p in PrimesUpTo(12222121) | Set(Intseq(p)) subset [1, 2]]; // _Vincenzo Librandi_, Jul 28 2012
%o (Python)
%o from sympy import primerange
%o def checkd(a, c):
%o b = set(int(i) for i in set(str(a)))
%o return b.issubset(c)
%o for n in primerange(2, 2000000):
%o if checkd(n, [1, 2]):
%o print(n)
%o # _Abhiram R Devesh_, May 08 2015
%Y Cf. A020449 (digits 0 & 1), ..., A020472 (digits 8 & 9). [From _M. F. Hasler_, Mar 18 2010]
%Y Subsequence of A007931.
%K nonn,base
%O 1,1
%A _David W. Wilson_
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