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 A169931 #12 Aug 17 2021 16:16:59
%S A169931 2,3,4,5,6,7,8,9,0,1,32,33,34,35,36,37,38,39,30,31,42,43,44,45,46,47,
%T A169931 48,49,40,41,52,53,54,55,56,57,58,59,50,51,62,63,64,65,66,67,68,69,60,
%U A169931 61,72,73,74,75,76,77,78,79,70,71,82,83,84,85,86,87,88,89,80,81,92,93,94,95,96
%N A169931 a(n) = 2*n in the arithmetic defined in A169918.
%C A169931 Equivalently, increase each (decimal) digit by 2 and take each result modulo 10. I.e., apply d -> (d+2 mod 10) to each digit of n. - _M. F. Hasler_, Mar 25 2015
%F A169931 A169931 = A048379 o A048379 (function A048379 applied twice). - _M. F. Hasler_, Mar 25 2015
%t A169931 Table[FromDigits[Mod[IntegerDigits[n]+2,10]],{n,0,100}] (* _Harvey P. Dale_, Aug 17 2021 *)
%o A169931 (PARI) A169931(n)=2*!n+apply(d->(d+2)%10,n=digits(n))*vector(#n,i,10^(#n-i)) \\ _M. F. Hasler_, Mar 25 2015
%Y A169931 Cf. A048379, A169918.
%K A169931 nonn,base
%O A169931 0,1
%A A169931 _David Applegate_, _Marc LeBrun_ and _N. J. A. Sloane_, Jul 20 2010