A281965 Number of sets of exactly n positive integers <= n+2 having a square element sum.

1, 1, 1, 2, 2, 2, 3, 4, 3, 3, 5, 4, 4, 5, 7, 5, 5, 9, 6, 6, 8, 9, 7, 7, 13, 8, 8, 12, 11, 9, 10, 15, 10, 10, 16, 13, 11, 14, 17, 12, 12, 20, 14, 13, 18, 19, 14, 15, 24, 15, 15, 22, 20, 16, 19, 26, 17, 17, 27, 20, 18, 23, 27, 19, 19, 33, 20, 20, 28, 27, 21, 23

Offset: 0

Author

Alois P. Heinz, Feb 03 2017

Keywords

• nonn
• look

Examples

			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}.
		

Links

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

Crossrefs

A diagonal of A281871.

Formula

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