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 A383639 #6 May 08 2025 22:41:49 %S A383639 1,7,31,91,97,291,331,391,397,931,2331,3331,3391,3931,5331,7331,7397, %T A383639 8397,9291,9331,23331,27397,32331,33391,33931,39291,39331,43331,48397, %U A383639 59291,68397,69291,93331,127397,159291,427397,439291,459291,469291,623331,632331 %N A383639 Left-truncatable happy numbers: every suffix is a happy number and no digits are zero. %C A383639 Happy numbers in which repeatedly deleting the most significant digit gives a happy number at every step until a single-digit happy number remains. Last term is a(170) = 9639326993331. %H A383639 Shyam Sunder Gupta, <a href="/A383639/b383639.txt">Table of n, a(n) for n = 1..170</a> %H A383639 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 A383639 Cf. A007770. %K A383639 nonn,base,fini,full %O A383639 1,2 %A A383639 _Shyam Sunder Gupta_, May 03 2025