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 A061905 #3 Oct 27 2023 22:00:46
%S A061905 7,8,13,14,16,19,22,23,24,25,27,29,31,33,34,35,36,38,41,42,46,47,52,
%T A061905 54,55,56,57,58,59,61,65,66,68,69,70,71,72,75,78,79,80,81,84,85,95,96,
%U A061905 99,103,104,106,108,112,115,119,121,123,129,130,131,132,135,138,139,140
%N A061905 The iterative cycle: n -> sum of digits of n^2 has only two distinct elements.
%C A061905 It seems that {10,1}, {13,16} and {9,18} are the only iterative cycles with 2 distinct elements.
%e A061905 7 -> 4+9 = 13 -> 1+6+9 = 16 -> 2+5+6 = 13, thus only {13,16} are contained in the iterative cycle of 7. 24 -> 5+7+6 = 18 -> 3+2+4 = 9 -> 8+1 = 9, thus {18,9} are the only elements of the iterative cycle of 24.
%Y A061905 Cf. A007953, A004159, A061903 - A061910.
%K A061905 nonn,base
%O A061905 1,1
%A A061905 _Asher Auel_, May 17 2001