A364484 Numbers whose prime factorization (prime factors and exponents) contains the digits 1 and 2 at least once, but no other digits.

2, 22, 44, 121, 211, 242, 422, 484, 844, 2048, 2111, 2221, 2321, 4096, 4222, 4442, 4642, 8444, 8884, 9284, 12211, 21121, 21211, 21221, 22111, 22528, 23221, 24422, 24431, 25531, 42242, 42422, 42442, 44222, 44521, 45056, 46442, 48844, 48862, 51062, 84484, 84844, 84884, 88444, 89042, 92884, 97724

Offset

1,1

Links

Table of n, a(n) for n=1..47.

Example

9284 is a term because 9284 = 2^2 * 11^1 * 211^1.

Prog

(PARI) for(n=1, 1e5, v=[]; s=Set(v); f=factor(n); k=#f[, 1]; for(i=1, k, s1=Set(digits(f[i, 1])); s=setunion(s, s1)); for(i=1, k, s2=Set(digits(f[i, 2])); s=setunion(s, s2)); if(s==[1, 2], print1(n, ", ")))

Crossrefs

Cf. A007931.

Sequence in context: A154798 A350318 A080142 * A306969 A200946 A322157

Adjacent sequences: A364481 A364482 A364483 * A364485 A364486 A364487

Keyword

nonn,base

Author

Alexandru Petrescu, Jul 26 2023

Status

approved