Program to generate the b file for A339608

b339608-gen.py

#!/usr/bin/python

# Encode a natural number (incl 0) as a bijective number (string)
def bijEnc(num, symbols="ab"):
    ret = ''
    slen = len(symbols)
    while num > 0:
        num -= 1
        ret = symbols[num % slen] + ret
        num = num // slen
    return ret

# Decode a bijective number (string) as a regular natural number
def bijDec(s, symbols="ab"):
    acc = 0
    for c in s:
        acc *= len(symbols)
        acc += (symbols.index(c) + 1)
    return acc

# Factor a string into its Lyndon words
def lyndonFactor(s):
    k = 0
    ret = []
    while k < len(s):
        i = k
        j = i + 1
        while j < len(s) and s[i] <= s[j]:
            if s[i] == s[j]:
                i += 1
            else:
                i = k
            j += 1
        
        oldk = k
        k = k + j - i
        ret.append(s[oldk:k])
    return ret

line_num=1
n = 1
while line_num <= 20000:
    factors = lyndonFactor(bijEnc(n))
    if len(factors) == 1:
        print(line_num, bijDec(factors[0]))
        line_num += 1
    n+=1

Run in python3 to generate the exact file (it kind of works in Python 2, but requires reformatting to be a proper B file).