Generate-and-count code for OEIS A271205 using NetworkX

generate_a271205.py

#!/usr/bin/env python3
import networkx as nx


def populate(table, n):
    treelist = nx.generators.nonisomorphic_trees(n)
    for tree in treelist:
        degrees = list(nx.degree(tree).values())
        if 2 not in degrees:
            l = degrees.count(1)
            if (l, n) not in table:
                table[(l, n)] = 0
            table[(l, n)] += 1


def output_line(table, l):
    print("l = %u: " % l, end='')
    for n in range(l+1, 2*l - 1):
        print("%u, " % table[(l, n)], end='')
        del table[(l, n)]
    print()


table = {}
n = 4
while True:
    populate(table, n)
    if n % 2 == 0:
        output_line(table, n//2 + 1)
    n += 1