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A273825
Table read by rows: the n-th row is the list of numbers diagonally up and to the left of n in the natural numbers read by antidiagonals.
5
1, 2, 3, 4, 5, 1, 6, 7, 8, 2, 9, 3, 10, 11, 12, 4, 13, 5, 1, 14, 6, 15, 16, 17, 7, 18, 8, 2, 19, 9, 3, 20, 10, 21, 22, 23, 11, 24, 12, 4, 25, 13, 5, 1, 26, 14, 6, 27, 15, 28, 29, 30, 16, 31, 17, 7, 32, 18, 8, 2, 33, 19, 9, 3, 34, 20, 10, 35, 21, 36, 37, 38, 22
OFFSET
1,2
EXAMPLE
A000027 read by antidiagonals is:
1 2 4 7
3 5 8
6 9
...
Thus:
Row 1: []
Row 2: []
Row 3: []
Row 4: []
Row 5: [1]
Row 6: []
Row 7: []
Row 8: [2]
Row 9: [3]
MATHEMATICA
nn = 58; t = Table[(n^2 - n)/2 + Accumulate@ Range[n - 1, Ceiling[(Sqrt[9 + 8 nn] - 3)/2]] + 1, {n, Ceiling[(Sqrt[9 + 8 nn] - 3)/2] + 1}]; Table[Rest@ Map[t[[#1, #2]] & @@ # &, Most@ NestWhileList[# - 1 &, #, ! MemberQ[#, 0] &]] &@ First@ Position[t, n], {n, nn}] // Flatten (* Michael De Vlieger, Jun 29 2016 *)
PROG
(Haskell)
a273825 n = genericIndex a273825_list (n - 1)
a273825_list = concatMap a273825_row [1..]
a273825_tabf = map a273825_row [1..]
a273825_row n
| a_i == 0 = []
| otherwise = a_i : a273825_row a_i where
a_i = a271439 $ a271439 (n - 1)
KEYWORD
nonn,tabf
AUTHOR
Peter Kagey, Jun 08 2016
STATUS
approved