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 A194041 #12 Feb 16 2025 08:33:15
%S A194041 3,9,15,21,25,33,37,43,51,63,67,69,73,75,87,93,99,105,111,115,127,135,
%T A194041 141,151,159,163,169,171,189,195,201,205,211,223,231,235,237,241,259,
%U A194041 261,267,273,283,285,289,297,303,307,321,327,339,349,357,361,385,393
%N A194041 Lucky numbers which are also unhappy numbers.
%C A194041 An unhappy number is a number that is not happy (A007770) i.e., a number n such that iterating this sum-of-squared-digits map starting with n never reaches the number 1. Many asymptotic properties of the prime numbers are shared by the lucky numbers.
%H A194041 Nathaniel Johnston, <a href="/A194041/b194041.txt">Table of n, a(n) for n = 1..1000</a>
%H A194041 Eric W. Weisstein, <a href="https://mathworld.wolfram.com/UnhappyNumber.html">Unhappy Number</a>
%H A194041 Eric W. Weisstein, <a href="https://mathworld.wolfram.com/LuckyNumber.html">Lucky Number</a>
%F A194041 A000959 INTERSECTION A031177. {k such that k is in A000959 and k is not in A007770}.
%Y A194041 Cf. A000959, A007770, A031177.
%K A194041 nonn,easy
%O A194041 1,1
%A A194041 _Jonathan Vos Post_, Aug 12 2011