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 A020450 Primes that contain digits 1 and 2 only. 10
 2, 11, 211, 2111, 2221, 12211, 21121, 21211, 21221, 22111, 111121, 111211, 112111, 112121, 1111211, 1121221, 1212121, 1212221, 1221221, 2121121, 2211211, 2221111, 11221211, 12111221, 12121121, 12121211, 12122111, 12122221, 12212111, 12222121 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Flatten[Table[Select[FromDigits/@Tuples[{1, 2}, n], PrimeQ], {n, 8}]] (* Vincenzo Librandi, Jul 28 2012 *) PROG (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 (Magma) [p: p in PrimesUpTo(12222121) | Set(Intseq(p)) subset [1, 2]]; // Vincenzo Librandi, Jul 28 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, 2]): print(n) # Abhiram R Devesh, May 08 2015 CROSSREFS Cf. A020449 (digits 0 & 1), ..., A020472 (digits 8 & 9). [From M. F. Hasler, Mar 18 2010] Subsequence of A007931. Sequence in context: A188203 A070256 A356523 * A036229 A104337 A283512 Adjacent sequences: A020447 A020448 A020449 * A020451 A020452 A020453 KEYWORD nonn,base AUTHOR David W. Wilson STATUS approved

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Last modified July 23 08:23 EDT 2024. Contains 374546 sequences. (Running on oeis4.)