A284323 Numbers n such that product of digits of n is a power of 4.

1, 4, 11, 14, 22, 28, 41, 44, 82, 88, 111, 114, 122, 128, 141, 144, 182, 188, 212, 218, 221, 224, 242, 248, 281, 284, 411, 414, 422, 428, 441, 444, 482, 488, 812, 818, 821, 824, 842, 848, 881, 884, 1111, 1114, 1122, 1128, 1141, 1144, 1182, 1188, 1212, 1218

Offset

0,2

Comments

Supersequence of A032822.

Links

Table of n, a(n) for n=0..51.

Example

1111 is in the sequence because 1*1*1*1 = 1 = 4^0.

Mathematica

FromDigits /@ Select[Join @@ Map[Tuples[2^Range[0, 3], #] &, Range@ 4], IntegerQ@ Log[4, Times @@ #] &] (* Michael De Vlieger, Mar 25 2017 *)

Prog

(Magma) Set(Sort([n: n in [1..10000], k in [0..20] | &*Intseq(n) eq 4^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), this sequence (k = 4), A276037 (k = 5), A276038 (k = 6), A276039 (k = 7), A284324 (k = 8), A284295 (k = 9).

Sequence in context: A285979 A299975 A271508 * A352403 A091436 A032822

Adjacent sequences: A284320 A284321 A284322 * A284324 A284325 A284326

Keyword

nonn,base

Author

Jaroslav Krizek, Mar 25 2017

Status

approved