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 A215649 #26 Dec 23 2021 00:43:51
%S A215649 0,0,1,1,2,4,7,18,31,42,44,405,472,729,941,5071,6313,8675,9853,21066,
%T A215649 31591,90601,447014,514121,674557,713322,770074,4606468,7359831,
%U A215649 7575552,8089735,19520951,52494292,69005989,106799181,474396516,777547433,2586342311,3016782802
%N A215649 Reversals of tribonacci numbers (sorted).
%C A215649 This is to A004170 as tribonacci numbers A000073 are to Fibonacci numbers A000045. Note that tribonacci(20) = 35890 is, upon reversal, 09853, then the leading 0 is truncated, making the 5-digit number into the 4-digit number 9853. Similarly, R(4700770) = 770074.
%H A215649 Harvey P. Dale, <a href="/A215649/b215649.txt">Table of n, a(n) for n = 0..1000</a>
%e A215649 A000073(n) for n = 7, 8, 9 = 13, 24, 44, 81. Reversed, those are 31, 42, 44, 18, and sorted that is 18, 31, 42, 44.
%t A215649 Sort[FromDigits[Reverse[IntegerDigits[#]]]&/@LinearRecurrence[{1,1,1},{0,0,1,1},40]] (* _Harvey P. Dale_, Nov 22 2015 *)
%Y A215649 Cf. A000045, A000073, A004086, A004170, A004091, A140463, A214855, A004086.
%K A215649 nonn,base,easy
%O A215649 0,5
%A A215649 _Jonathan Vos Post_, Mar 09 2013