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 A257950 #15 Nov 30 2019 17:22:19 %S A257950 1,10,100,103,301,367,608,806,1000,1030,3010,3056,5630,6080,6703,6791, %T A257950 8060,9167,10000,10003,10275,10300,11241,12770,12939,13929,14112, %U A257950 17027,17502,20175,21921,22119,27501,30001,30067,30100,30616,31606,36700 %N A257950 Numbers n which are both happy (A007770) and bihappy (A257795) numbers. %C A257950 This sequence is infinite, because it contains infinite subsequences (powers of 10, for example). %H A257950 Giovanni Resta, <a href="/A257950/b257950.txt">Table of n, a(n) for n = 1..10000</a> %F A257950 All 10^k are members of this sequence. %F A257950 If n is a member each permutation of a set of pairs of digits gives another members (example 367 and 6703). %F A257950 Placing two zeros between the sets of two digits gives another member. %e A257950 367 is member of this sequence because 367 = 3^2+6^2+7^2= 94 => 9^2+4^2 = 97 => 9^2+7^2 = 130 => 1^2+3^2+0^2 = 10 => 1^2+0^2 = 1, so after five iterations 367 reaches 1. And 3^2+67^2 = 4498 => 44^2+98^2= 11540 => 1^2+15^2+40^2 = 1826 => 18^2+26^2 = 1000 => 10^2+0^2 = 100 =>1^2+0^2 = 1, so in 6 iterations 367 reaches 1. %Y A257950 Cf. A007770, A257795. %K A257950 nonn,base %O A257950 1,2 %A A257950 _Pieter Post_, May 14 2015