

A069571


Numbers n in which the kth digit (counted from the right) is nonzero and is either a divisor of k (but not 1 in case k has a single digit prime divisor) or a multiple of k, for all 1 <= k <= number of digits of n.


4



1, 2, 3, 4, 5, 6, 7, 8, 9, 21, 22, 23, 24, 25, 26, 27, 28, 29, 41, 42, 43, 44, 45, 46, 47, 48, 49, 61, 62, 63, 64, 65, 66, 67, 68, 69, 81, 82, 83, 84, 85, 86, 87, 88, 89, 321, 322, 323, 324, 325, 326, 327, 328, 329, 341, 342, 343, 344, 345, 346, 347, 348, 349, 361, 362
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OFFSET

1,2


COMMENTS

This is the subsequence of terms of A069570 with no digit 1 elsewhere than (possibly) in positions k with no prime divisor < 10, i.e., k = 1, 11, 13, 17, 19, ..., 11*11, 127, 131, 137, 139, 11*13, ....  M. F. Hasler, Sep 27 2016


LINKS

Table of n, a(n) for n=1..65.


EXAMPLE

54647 is a member but 14647 and 44647 are not members.
13 is a member of A069570 because both 1 and 3 are nonzero, further, 3 is divisible by n = 1 and 1 divides n = 2. 13 is not a member of this sequence because it has a single digit multiple 3 > 1.
Numbers with "1" in place n = 1 may be in the sequence since 1 divides itself, and 1 does not exceed 1.
21 is a member of this sequence because the digits are nonzero, 1 divides n = 1 and 2 divides n = 2.


MATHEMATICA

Select[Range@ 400, Times @@ Map[Boole, MapIndexed[If[Or[#1 == 0, And[First@ #2 > 1, #1 == 1]], False, Total@ Boole@ {First@ Divisible[#2, #1], First@ Divisible[#1, #2]} > 0] &, Reverse@ IntegerDigits@ #]] > 0 &] (* Michael De Vlieger, Sep 28 2016 *)


CROSSREFS

Cf. A069570.
Sequence in context: A076105 A094280 A082323 * A039173 A103951 A098951
Adjacent sequences: A069568 A069569 A069570 * A069572 A069573 A069574


KEYWORD

nonn,base


AUTHOR

Amarnath Murthy, Mar 24 2002


EXTENSIONS

Definition clarified by M. F. Hasler, Sep 27 2016
Edited by N. J. A. Sloane, Oct 02 2016


STATUS

approved



