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 A193567 #18 Feb 16 2025 08:33:15 %S A193567 3,9,18,30,33,37,39,47,56,57,59,61,65,74,75,81,90,93,95,106,108,111, %T A193567 114,122,125,137,138,141,144,148,152,157,158,160,173,175,178,180,183, %U A193567 184,185,187,212,215,221,225,227,246,251,252,256,258,264,265,272,285 %N A193567 Unhappy numbers which enter the cycle (4, 16, 37, 58, 89, 145, 42, 20) at 37. %H A193567 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/UnhappyNumber.html">Unhappy Number</a>. %e A193567 568 is such a number of height 7 because it enters the cycle at 37 in 7 steps: 568 -> 125 -> 30 -> 9 -> 81 -> 65 -> 61 -> 37 -> 58 -> 89 -> 145 -> 42 -> 20 -> 4 -> 16 -> 37 -> ... %p A193567 S:=proc(n) local Q,k,N,z; Q:=[n]; for k from 1 do N:=convert(Q[k],base,10); z:=sum(N['i']^2,'i'=1..nops(N)); if not member(z,Q) then Q:=[op(Q),z]; else Q:=[op(Q),z]; break; fi; od; return Q; end: %p A193567 a:=[]: for i from 1 while nops(a)<30 do Q:=S(i); A:=Q[nops(Q)]; if A=37 then a:=[op(a),i] fi; od: print(op(a)); %Y A193567 Cf. A031177, A039943. %K A193567 nonn,base %O A193567 1,1 %A A193567 _Martin Renner_, Jul 31 2011