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.
%I A347298 #28 Mar 17 2025 05:38:02
%S A347298 20,21,22,40,41,42,43,44,60,61,62,63,64,65,66,80,81,82,83,84,85,86,87,
%T A347298 88,100,120,121,122,140,141,142,143,144,160,161,162,163,164,165,166,
%U A347298 180,181,182,183,184,185,186,187,188,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215
%N A347298 Numbers that contain an even digit d immediately followed by a digit <= d.
%C A347298 Conjecture: This is precisely the list of numbers missing from A342042.
%C A347298 The conjecture is correct, see A342042 for details. - _Sebastian Karlsson_, Oct 02 2021
%H A347298 Paolo Xausa, <a href="/A347298/b347298.txt">Table of n, a(n) for n = 1..10000</a>
%t A347298 A347298Q[k_] := MemberQ[Partition[IntegerDigits[k], 2, 1], {i_?EvenQ, j_} /; j <= i];
%t A347298 Select[Range[300], A347298Q] (* _Paolo Xausa_, Mar 17 2025 *)
%o A347298 (Python)
%o A347298 def ok(n):
%o A347298 s = str(n)
%o A347298 return any(s[i] in "2468" and s[i+1] <= s[i] for i in range(len(s)-1))
%o A347298 print([k for k in range(216) if ok(k)]) # _Michael S. Branicky_, Nov 28 2024
%Y A347298 Cf. A342042, A377912 (complement).
%K A347298 nonn,base
%O A347298 1,1
%A A347298 _N. J. A. Sloane_, Aug 26 2021