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A343853
Irregular triangle read by rows: the n-th row gives the row indices of the matrix of 1..n^2 filled successively back and forth along antidiagonals.
2
1, 1, 1, 2, 2, 1, 1, 2, 3, 2, 1, 2, 3, 3, 1, 1, 2, 3, 2, 1, 1, 2, 3, 4, 4, 3, 2, 3, 4, 4, 1, 1, 2, 3, 2, 1, 1, 2, 3, 4, 5, 4, 3, 2, 1, 2, 3, 4, 5, 5, 4, 3, 4, 5, 5, 1, 1, 2, 3, 2, 1, 1, 2, 3, 4, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 3, 4, 5, 6, 6, 5, 4, 5, 6, 6
OFFSET
1,4
EXAMPLE
The triangle begins:
1
1 1 2 2
1 1 2 3 2 1 2 3 3
1 1 2 3 2 1 1 2 3 4 4 3 2 3 4 4
...
MATHEMATICA
a={}; For[n=1, n<=6, n++, For[d=1, d<=n, d++, If[OddQ[d], i=d; For [k=1, k<=d, k++, AppendTo[a, i-k+1]], i=1; For[k=1, k<=d, k++, AppendTo[a, i+k-1]]]]; For[d=n+1, d<=2n-1, d++, If[OddQ[d], i= n; For[k=1, k<=2n-d, k++, AppendTo[a, i-k+1]], If[EvenQ[d], i=d-n+1; For[k=1, k<=2n-d, k++, AppendTo[a, i+k-1]]]]]]; a
CROSSREFS
Cf. A000290 (row length), A002411 (row sums), A060747 (number of antidiagonals), A078475, A319573, A343854 (column indices).
Sequence in context: A193596 A275420 A344961 * A143974 A301565 A237265
KEYWORD
nonn,look,tabf
AUTHOR
Stefano Spezia, May 01 2021
STATUS
approved