The three types of terms of the Lambda-Calculus can be categorised by various constraints.
One such constraints is the the length of their standart representation.
This program counts the number of closed Lambda terms with a given length.
This implementation is currently by far the best.
ref OEIS A260661.

docker run --rm -it ggwpez/lambda_counter 100

You will need GNU GMP, its the big numbers libary used.
Download it from here or install the package libgmp-dev.

git clone https://github.com/ggwpez/Lambda-Counter && cd Lambda-Counter && make

It takes two arguments; the start and the end. It caluculates the values in range [start, end] .
The start can be omitted in which case it is defaulted to 0. Example:

./lambda_counter 10 100

Can be cancelled with Ctrl+C.
100.txt contains the output for [0, 100].

Licensed under GPLv3, see LICENSE file.
Copyright 2016-2021 Oliver Tale-Yazdi oliver@tasty.limo.