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A069571 Numbers n in which the k-th 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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 23 19:17 EDT 2017. Contains 283957 sequences.