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 A193571 #18 Feb 16 2025 08:33:15 %S A193571 42,154,389,398,415,451,514,541,839,893,938,983,1045,1054,1126,1162, %T A193571 1216,1261,1344,1405,1434,1443,1450,1504,1540,1588,1612,1621,1669, %U A193571 1696,1858,1885,1966,2116,2161,2235,2253,2325,2352,2523,2532,2611,3089,3098,3144 %N A193571 Unhappy numbers which enter the cycle (4, 16, 37, 58, 89, 145, 42, 20) at 42. %H A193571 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/UnhappyNumber.html">Unhappy Number</a>. %e A193571 389 is such a number of height 2 because it enters the cycle at 42 in 2 steps: 389 -> 154 -> 42 -> 20 -> 4 -> 16 -> 37 -> 58 -> 89 -> 145 -> 42 -> ... %p A193571 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 A193571 a:=[]: for i from 1 while nops(a)<30 do Q:=S(i); A:=Q[nops(Q)]; if A=42 then a:=[op(a),i] fi; od: print(op(a)); %Y A193571 Cf. A031177, A039943. %K A193571 nonn,base %O A193571 1,1 %A A193571 _Martin Renner_, Jul 31 2011