This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
a262367 n = a262367_list !! (n-1) a262367_list = [x | x <- [1..], a262323 x == x]
The first terms of the sequence are: +----+---------+ | n | a(n) | +----+---------+ | 1 | 1 | | 2 | 10 | | 3 | 11 | | 4 | 12 | | 5 | 2 | | 6 | 20 | | 7 | 22 | | 8 | 21 | | 9 | 13 | | 10 | 3 | | 11 | 23 | | 12 | 30 | | 13 | 33 | | 14 | 31 | | 15 | 14 | | 16 | 4 | | 17 | 24 | | 18 | 32 | | 19 | 25 | | 20 | 5 | +----+---------+
import Data.List (inits, tails, intersect, delete)
a262323 n = a262323_list !! (n-1)
a262323_list = 1 : f "1" (map show [2..]) where
f xs zss = g zss where
g (ys:yss) | null (intersect its $ tail $ inits ys) &&
null (intersect tis $ init $ tails ys) = g yss
| otherwise = (read ys :: Int) : f ys (delete ys zss)
its = init $ tails xs; tis = tail $ inits xs
-- Reinhard Zumkeller, Sep 21 2015
See Links section.
def overlaps(a, b):
s, t = sorted([str(a), str(b)], key = lambda x: len(x))
if any(t.startswith(s[i:]) for i in range(len(s))): return True
return any(t.endswith(s[:i]) for i in range(1, len(s)+1))
def aupto(nn):
alst, aset = [1], {1}
for n in range(2, nn+1):
an = 1
while True:
while an in aset: an += 1
if overlaps(an, alst[-1]): alst.append(an); aset.add(an); break
an += 1
return alst
print(aupto(67)) # Michael S. Branicky, Jan 10 2021
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