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A335490 Isosceles triangle read by rows in which each term is the least positive integer satisfying the condition that no row, diagonal, or antidiagonal contains a repeated term. 0
1, 2, 3, 3, 1, 2, 4, 2, 3, 5, 5, 6, 1, 4, 7, 6, 4, 5, 7, 8, 9, 7, 5, 6, 1, 4, 10, 8, 8, 9, 4, 2, 3, 5, 6, 10, 9, 7, 8, 3, 1, 2, 10, 5, 4, 10, 8, 9, 6, 2, 3, 7, 11, 12, 13, 11, 12, 7, 10, 5, 1, 9, 8, 6, 14, 15, 12, 10, 11, 13, 6, 4, 14, 7, 9, 8, 16, 17, 13, 11 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The n-th instance of 1 occurs at index A001844(n-1).

Records occur at 1, 2, 3, 7, 10, 12, 15, 20, 21, 27, 53, 54, 55, 65, ...

LINKS

Table of n, a(n) for n=1..80.

FORMULA

a(n) = A296339(n-1) + 1. - Rémy Sigrist, Sep 13 2020

EXAMPLE

Triangle begins:

       1

      2 3

     3 1 2

    4 2 3 5

   5 6 1 4 7

  6 4 X ...

The value for X is 5 because 1, 2, and 3 are on the diagonal; 4 and 6 are on the antidiagonal; and 4 and 6 are in the row. Therefore 5 is the smallest value that can be inserted so that no diagonal, antidiagonal, or row contains a repeated term.

CROSSREFS

Analogs for other tilings: A269526 (square), A334049 (triangular).

Cf. A001844, A274650, A274651, A288530, A288531, A296339.

Sequence in context: A066517 A108132 A106589 * A334290 A294101 A051911

Adjacent sequences:  A335487 A335488 A335489 * A335491 A335492 A335493

KEYWORD

tabl,nonn,more

AUTHOR

Alec Jones and Peter Kagey, Sep 12 2020

STATUS

approved

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Last modified October 21 02:25 EDT 2021. Contains 348141 sequences. (Running on oeis4.)