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

1,2

Comments

Illustrated with other convex polyabolos in A245676.

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Andrew Howroyd, Convex Quadrilaterals formed from Polyabolos

Example

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

Prog

(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

Crossrefs

Strictly less than A245676.

Sequence in context: A068066 A171889 A171868 * A334685 A340694 A101910

Adjacent sequences: A292143 A292144 A292145 * A292147 A292148 A292149

Keyword

nonn

Author

Douglas J. Durian, Sep 09 2017

Extensions

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

Status

approved