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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 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 A342304 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 May 17 22:15 EDT 2021. Contains 343992 sequences. (Running on oeis4.)