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 A230725 #13 Mar 18 2025 15:30:04
%S A230725 1,1,1,3,5,9,8,4,12,6,13,13,14,4,13,13,21,20,18,32,25,21,33,25,43,20,
%T A230725 16,25,16,21,53,36,38,46,48,51,46,64,44,55,46,46,48,41,45,53,58,57,60,
%U A230725 49,58,59,67,58,76,57,65,72,77,61
%N A230725 Digital sum of tribonacci numbers with a(0)=a(1)=a(2)=1.
%H A230725 Irene Sermon, <a href="/A230725/b230725.txt">Table of n, a(n) for n = 0..10000</a>
%F A230725 a(n) = A007953(A000213(n)).
%e A230725 In the tribonacci sequence with initial values a(0)=a(1)=a(2)=1, the 30th term is 37895489. Its digital sum is 53.
%t A230725 Total[IntegerDigits[#]]&/@LinearRecurrence[{1,1,1},{1,1,1},60] (* _Harvey P. Dale_, Mar 18 2025 *)
%o A230725 (Sage)
%o A230725 L=[1,1,1]
%o A230725 n=100 #change for more terms
%o A230725 for i in [3..n]:
%o A230725 L.append(L[i-3]+L[i-2]+L[i-1])
%o A230725 [sum(x.digits(base=10)) for x in L] # _Tom Edgar_, Nov 09 2013
%Y A230725 Cf. A000213.
%K A230725 nonn,base
%O A230725 0,4
%A A230725 _Irene Sermon_, Oct 28 2013