A284295 Numbers n such that product of digits of n is a power of 9.

1, 9, 11, 19, 33, 91, 99, 111, 119, 133, 191, 199, 313, 331, 339, 393, 911, 919, 933, 991, 999, 1111, 1119, 1133, 1191, 1199, 1313, 1331, 1339, 1393, 1911, 1919, 1933, 1991, 1999, 3113, 3131, 3139, 3193, 3311, 3319, 3333, 3391, 3399, 3913, 3931, 3939, 3993

Offset

1,2

Comments

Supersequence of A284294.

Links

Table of n, a(n) for n=1..48.

Example

1111 is in the sequence because 1*1*1*1 = 1 = 9^0.

Mathematica

FromDigits /@ Select[Join @@ Map[Tuples[{1, 3, 9}, #] &, Range@ 4], IntegerQ@ Log[9, Times @@ #] &] (* Michael De Vlieger, Mar 25 2017 *)

Prog

(Magma) Set(Sort([n: n in [1..10000], k in [0..20] | &*Intseq(n) eq 9^k]))

Crossrefs

Cf. Numbers n such that product of digits of n is a power of k for k = 0 - 9: A284375 (k = 0), A002275 (k = 1), A028846 (k = 2), A174813 (k = 3), A284323 (k = 4), A276037 (k = 5), A276038 (k = 6), A276039 (k = 7), A284324 (k = 8), this sequence (k = 9).

Sequence in context: A090771 A329279 A372242 * A284294 A195572 A046259

Adjacent sequences: A284292 A284293 A284294 * A284296 A284297 A284298

Keyword

nonn,base

Author

Jaroslav Krizek, Mar 25 2017

Status

approved