1,2

Diagonal of A216031.

Table of n, a(n) for n=1..6.

Some solutions for n=4

..x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..1

..2..x..3..x....0..x..2..x....2..x..3..x....2..x..3..x....2..x..3..x

..x..3..x..4....x..1..x..0....x..3..x..0....x..4..x..2....x..1..x..4

..3..x..0..x....3..x..0..x....4..x..2..x....5..x..2..x....1..x..0..x

Cf. A216031.

Sequence in context: A012557 A012562 A263959 * A247220 A012753 A012440

Adjacent sequences: A216021 A216022 A216023 * A216025 A216026 A216027

nonn

R. H. Hardin, Aug 30 2012

approved