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 A338839 #14 Nov 19 2020 23:56:01 %S A338839 0,2,4,16,6,14,8,12,10,18,22,20,24,36,26,34,28,32,30,38,42,40,44,156, %T A338839 46,154,48,152,50,150,52,148,54,146,56,144,58,142,60,140,62,138,64, %U A338839 136,66,134,68,132,70,130,72,128,74,126,76,124,78,122,80,120,82,118,84,116,86,114,88,112,90,110,92 %N A338839 No odd digit is present in a(n) + a(n+1). %C A338839 This is the lexicographically earliest sequence of distinct nonnegative terms with this property. %H A338839 Carole Dubois, <a href="/A338839/b338839.txt">Table of n, a(n) for n = 1..9999</a> %e A338839 a(1) + a(2) = 0 + 2 = 2 (no odd digit is present); %e A338839 a(2) + a(3) = 2 + 4 = 6 (no odd digit is present); %e A338839 a(3) + a(4) = 4 + 16 = 20 (no odd digit is present); etc. %t A338839 Block[{a = {0}}, Do[Block[{k = 2}, While[Nand[FreeQ[a, k], AllTrue[IntegerDigits@ Total[a[[-1]] + k], EvenQ]], k += 2]; AppendTo[a, k]], {i, 2, 71}]; a] (* _Michael De Vlieger_, Nov 12 2020 *) %Y A338839 Cf. A014263 (no odd digit). %Y A338839 Cf. A338840, A338841, A338842, A338843, A338844, A338845, A338846 (variants on the same idea). %K A338839 base,nonn %O A338839 1,2 %A A338839 _Eric Angelini_ and _Carole Dubois_, Nov 11 2020