A211312 Square array of Delannoy numbers D(i,j) mod 3 (i >= 0, j >= 0) read by antidiagonals.
1, 1, 1, 1, 0, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 2, 2, 0, 2, 2, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 1, 2, 2, 2, 0, 0, 2, 2, 2, 1, 1, 1, 1, 2, 2, 0, 2, 2, 1, 1, 1, 1, 0, 1, 2, 0, 2, 2, 0, 2, 1, 0, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1
Offset: 0
Examples
Written as a triangle: 1, 1, 1, 1, 0, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 2, 2, 0, 2, 2, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, ...
Links
- Marko Razpet, A self-similarity structure generated by king's walk, Algebraic and topological methods in graph theory (Lake Bled, 1999). Discrete Math. 244 (2002), no. 1-3, 423--433. MR1844050 (2002k:05022)
- Rémy Sigrist, Colored representation of the first 1000 rows
Programs
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Maple
A211312 := proc(n,k): add(binomial(k, j) * binomial(n-j, k), j=0..n-k) mod 3 end: seq(seq(A211312(n,k), k=0..n), n=0..12); # Johannes W. Meijer, Jul 19 2013
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Mathematica
a[n_, k_] := Mod[Binomial[n, k]*Hypergeometric2F1[-k, k-n, -n, -1], 3]; Table[a[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 14 2014, after Johannes W. Meijer *)
Formula
a(n) = sum(binomial(k, j) * binomial(n-j, k), j=0..n-k) mod 3. - Johannes W. Meijer, Jul 19 2013