0,4

Alois P. Heinz, Table of n, a(n) for n = 0..1000

a(n) = A281871(n+2,n).

a(7) = 4: {1,2,3,6,7,8,9}, {1,2,4,5,7,8,9}, {1,3,4,5,6,8,9}, {2,3,4,5,6,7,9}.

a(8) = 3: {1,2,3,4,5,6,7,8}, {1,3,5,6,7,8,9,10}, {2,3,4,6,7,8,9,10}.

a(9) = 3: {1,2,3,4,5,6,7,10,11}, {1,2,3,4,5,6,8,9,11}, {1,2,3,4,5,7,8,9,10}.

A diagonal of A281871.

Sequence in context: A178065 A057748 A057747 * A228074 A152803 A187181

Adjacent sequences: A281962 A281963 A281964 * A281966 A281967 A281968

nonn,look

Alois P. Heinz, Feb 03 2017

approved