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 A074858 #16 Apr 05 2020 13:02:08
%S A074858 1,1,1,3,5,9,17,31,57,159,229,463,1643,3028,5035,11524,24762,41591,
%T A074858 108864,177197,305575,951573,2048919,3575995,6000073,18774470,
%U A074858 30770296,53244772,91462849,213915324,333122408,641864151,1398505871,2844591355
%N A074858 a(n) = a(n-1) + a(n-2) + R(a(n-3)) where a(0) = a(1) = a(2) = 1 and R(n) (A004086) means the reverse of n.
%H A074858 Harvey P. Dale, <a href="/A074858/b074858.txt">Table of n, a(n) for n = 0..1000</a>
%e A074858 a(9) = 57 + 31 + R(17) = 57 + 31 + 71 = 159.
%p A074858 R:=proc(n) local nn, nnn: nn:=convert(n,base,10): add(nn[nops(nn)+1-j]*10^(j-1),j=1..nops(nn)) end: a[0]:=1: a[1]:=1: a[2]:=1: for n from 3 to 34 do a[n]:=a[n-1]+a[n-2]+R(a[n-3]) od: seq(a[n],n=0..34); # _Emeric Deutsch_, Jul 25 2005
%t A074858 RecurrenceTable[{a[0]==a[1]==a[2]==1,a[n]==a[n-1]+a[n-2]+IntegerReverse[ a[n-3]]},a,{n,40}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 05 2020 *)
%Y A074858 Cf. A000213.
%K A074858 easy,nonn,base
%O A074858 0,4
%A A074858 _Felice Russo_, Sep 11 2002
%E A074858 More terms from _Emeric Deutsch_, Jul 25 2005