A257471 Sequence obtained from A003991 (multiplication table read by antidiagonals) by removing repetitions.

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

Offset

1,2

Comments

A permutation of positive integers.

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Index entries for sequences that are permutations of the natural numbers

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 * A369136 A053212 A368108

Adjacent sequences: A257468 A257469 A257470 * A257472 A257473 A257474

Keyword

nonn,easy,look

Author

Ivan Neretin, Apr 25 2015

Status

approved