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 A257471 Sequence obtained from A003991 (multiplication table read by antidiagonals) by removing repetitions. 2
 1, 2, 3, 4, 6, 5, 8, 9, 10, 12, 7, 15, 16, 14, 18, 20, 21, 24, 25, 28, 30, 11, 27, 32, 35, 36, 22, 40, 42, 13, 33, 45, 48, 49, 26, 44, 50, 54, 56, 39, 55, 60, 63, 64, 52, 66, 70, 72, 17, 65, 77, 80, 81, 34, 78, 84, 88, 90, 19, 51, 75, 91, 96, 99, 100 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A permutation of positive integers. LINKS Ivan Neretin, Table of n, a(n) for n = 1..10000 EXAMPLE The infinite multiplication table 1...2...3...4...5... 2...4...6...8..10... 3...6...9..12..15... 4...8..12..16..20... 5..10..15..20..25... ... reads by antidiagonals as follows: 1, 2, 2, 3, 4, 3, 4, 6, 6, 4, 5, 8, 9, 8, 5, ... (A003991). By removing all numbers that were encountered previously, we get 1, 2, 3, 4, 6, 5, 8, 9, ... MATHEMATICA DeleteDuplicates[Flatten[Table[i * (n - i), {n, 20}, {i, n - 1}]]] CROSSREFS Cf. A003991 (multiplication table), A257472 (inverse permutation). Sequence in context: A084287 A263265 A263267 * A053212 A095424 A194507 Adjacent sequences:  A257468 A257469 A257470 * A257472 A257473 A257474 KEYWORD nonn,easy,look AUTHOR Ivan Neretin, Apr 25 2015 STATUS approved

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Last modified February 18 03:44 EST 2020. Contains 332006 sequences. (Running on oeis4.)