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 A383638 #9 May 08 2025 22:44:26 %S A383638 1,7,13,19,79,133,139,192,193,793,1332,1333,1335,1337,1339,1393,1929, %T A383638 1933,7937,7938,13323,13332,13334,13339,13393,13933,19293,19295,19296, %U A383638 19333,79372,79384,79386,133236,133326,133399,133939,139339,192934,192951,192954 %N A383638 Right-truncatable happy numbers: every prefix is a happy number and no digits are zero. %C A383638 Happy numbers in which repeatedly deleting the least significant digit gives a happy number at every step until a single-digit happy number remains. Last term is a(170) = 1933396239639. %H A383638 Shyam Sunder Gupta, <a href="/A383638/b383638.txt">Table of n, a(n) for n = 1..170</a> %H A383638 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_7">Happy Numbers</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 7, 209-222. %Y A383638 Cf. A007770. %K A383638 nonn,base,fini,full %O A383638 1,2 %A A383638 _Shyam Sunder Gupta_, May 03 2025