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 A033901 #16 Feb 03 2025 05:39:43 %S A033901 21,33,66,132,255,510,525,780,858,1446,2892,5181,6339,9708,10497, %T A033901 11976,23655,47211,58458,104046,105492,117951,229530,251889,377778, %U A033901 755556,1311123,2422356,4645812,5890380,5926269,8182968,9451857,10907646 %N A033901 Sort then Add, a(1)=21. %H A033901 Harvey P. Dale, <a href="/A033901/b033901.txt">Table of n, a(n) for n = 1..1000</a> %F A033901 a(n)=A033898(n+1), n>1. [From _R. J. Mathar_, Oct 22 2008] %p A033901 A033901 := proc(n) %p A033901 option remember ; %p A033901 if n =1 then %p A033901 21; %p A033901 else %p A033901 A070196(procname(n-1)) ; %p A033901 end if; %p A033901 end proc: %p A033901 seq(A033901(n),n=1..100) ; # _R. J. Mathar_, Feb 03 2025 %t A033901 NestList[FromDigits[Sort[IntegerDigits[#]]]+#&,21,40] (* _Harvey P. Dale_, Feb 23 2023 *) %Y A033901 Cf. A033860. %K A033901 nonn,base,easy %O A033901 1,1 %A A033901 _N. J. A. Sloane_, _David W. Wilson_