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 A294688 #18 Dec 27 2023 23:44:22 %S A294688 1,2,3,4,6,9,88,595 %N A294688 Palindromes in Narayana's cows sequence (A000930). %C A294688 595 is probably the last term. %p A294688 a := proc(n) if n < 4 then n else %p A294688 simplify(hypergeom([-n/3, (1-n)/3, (-1-n)/3], [-n/2, (-1-n)/2], -27/4)); %p A294688 convert(%, base, 10); ListTools:-Reverse(%); %p A294688 if %% = % then add(%[k]*10^(k-1), k=1..nops(%)) else NULL fi fi end: %p A294688 seq(a(n), n=1..200); # _Peter Luschny_, Nov 07 2017 %Y A294688 Cf. A000930, A002113, A045504, A055391. %K A294688 nonn,base,more,hard %O A294688 1,2 %A A294688 _Chai Wah Wu_, Nov 06 2017