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 A329850 Lexicographically earliest sequence of distinct positive integers such that for any n > 0, f(n) * f(a(n)) = f(n * a(n)) where f(m) is the product of the digits of m. 1
 1, 2, 3, 10, 19, 20, 30, 40, 50, 4, 60, 70, 18, 46, 80, 90, 100, 13, 5, 6, 64, 61, 28, 72, 102, 104, 62, 23, 41, 7, 110, 42, 120, 103, 106, 105, 109, 107, 130, 8, 29, 32, 140, 150, 108, 14, 160, 170, 180, 9, 190, 200, 201, 202, 83, 205, 210, 148, 204, 11, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence is a variant of A329804; both sequences share graphical features. This sequence is a self-inverse permutation of the positive integers. Keyword "look" added in view of the scatterplot of 110000 terms. - N. J. A. Sloane, Nov 23 2019 LINKS Rémy Sigrist, Table of n, a(n) for n = 1..21000 Rémy Sigrist, Scatterplot of the first 110000 terms Rémy Sigrist, C program for A329850 FORMULA a(a(n)) = n. EXAMPLE The first terms, alongside f(n), f(a(n)) and f(n*a(n)), are:   n   a(n)  f(n)  f(a(n))  f(n*a(n))   --  ----  ----  -------  ---------    1     1     1        1          1    2     2     2        2          4    3     3     3        3          9    4    10     4        0          0    5    19     5        9         45    6    20     6        0          0    7    30     7        0          0    8    40     8        0          0    9    50     9        0          0   10     4     0        4          0   11    60     1        0          0   12    70     2        0          0   13    18     3        8         24   14    46     4       24         96 PROG (C) See Links section. CROSSREFS Cf. A007954, A329804. Sequence in context: A143045 A156909 A215121 * A175569 A275020 A122822 Adjacent sequences:  A329847 A329848 A329849 * A329851 A329852 A329853 KEYWORD nonn,base,look AUTHOR Rémy Sigrist, Nov 22 2019 STATUS approved

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Last modified May 16 01:55 EDT 2021. Contains 343937 sequences. (Running on oeis4.)