A292146 Number of different convex quadrilaterals that can be formed from n congruent isosceles right triangles. Reflections are not counted as different.

0, 2, 2, 5, 2, 5, 3, 9, 2, 5, 2, 11, 2, 6, 4, 13, 3, 7, 2, 11, 4, 5, 3, 19, 2, 5, 4, 12, 2, 10, 3, 17, 4, 6, 4, 16, 2, 5, 4, 19, 3, 10, 2, 11, 6, 6, 3, 27, 3, 7, 4, 11, 2, 10, 4, 20, 4, 5, 2, 22, 2, 6, 7, 21, 4, 10, 2, 12, 4, 10, 3, 28, 3, 5, 6, 11, 4, 10

Offset: 1

Author

Douglas J. Durian, Sep 09 2017

Keywords

• nonn

Comments

Illustrated with other convex polyabolos in A245676.

Examples

			For n=2, there is a square and a parallelogram.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..1000
• Andrew Howroyd, Convex Quadrilaterals formed from Polyabolos

Crossrefs

Strictly less than A245676.

Programs

PARI

\\ here b is A100073
b(n) = if(n%2, floor(numdiv(n)/2), if(n%4, 0, floor(numdiv(n/4)/2)));
d(n) = my(t); sum(k=1, floor(sqrt((n-1)/2)), issquare(n+2*k^2,&t) && t>2*k);
a(n) = 2*b(n) + d(n) + if(n%2, 0, 2*numdiv(n/2) + b(n/2)) + if(n%4, 0, ceil(numdiv(n/4)/2)); \\ Andrew Howroyd, Sep 16 2017

Extensions

Terms a(33) and beyond from Andrew Howroyd, Sep 16 2017