OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = A281871(n+5,n).
EXAMPLE
a(2) = 4: {1,3}, {2,7}, {3,6}, {4,5}.
a(3) = 8: {1,2,6}, {1,3,5}, {1,7,8}, {2,3,4}, {2,6,8}, {3,5,8}, {3,6,7}, {4,5,7}.
a(4) = 14: {1,2,4,9}, {1,2,5,8}, {1,2,6,7}, {1,3,4,8}, {1,3,5,7}, {1,4,5,6}, {1,7,8,9}, {2,3,4,7}, {2,3,5,6}, {2,6,8,9}, {3,5,8,9}, {3,6,7,9}, {4,5,7,9}, {4,6,7,8}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 03 2017
STATUS
approved