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A284323 Numbers n such that product of digits of n is a power of 4. 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 (list; graph; refs; listen; history; text; internal format)
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 * A091436 A032822 A288316

Adjacent sequences:  A284320 A284321 A284322 * A284324 A284325 A284326

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Mar 25 2017

STATUS

approved

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Last modified October 18 00:21 EDT 2019. Contains 328135 sequences. (Running on oeis4.)