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 A138776 #4 Aug 12 2018 11:32:24
%S A138776 1,2,3,4,5,6,1,7,5,8,15,9,35,10,70,11,126,1,12,210,8,13,330,36,14,495,
%T A138776 120,15,715,330,16,1001,792,1,17,1365,1716,11,18,1820,3432,66,19,2380,
%U A138776 6435,286,20,3060,11440,1001
%N A138776 Triangle read by rows: T(n,k)=binomial(n-2k,3k+1) (n>=1, 0<=k<=(n-1)/5).
%C A138776 Row n contains floor((n+4)/5) terms.
%C A138776 Row sums yield A137357.
%D A138776 D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.4.
%p A138776 T:=proc(n,k) options operator, arrow: binomial(n-2*k, 3*k+1) end proc: for n to 20 do seq(T(n,k),k=0..(n-1)*1/5) end do; # yields sequence in triangular form
%t A138776 Table[Binomial[n-2k,3k+1],{n,30},{k,0,(n-1)/5}]//Flatten (* _Harvey P. Dale_, Aug 12 2018 *)
%Y A138776 Cf. A137357.
%K A138776 nonn,tabf
%O A138776 1,2
%A A138776 _Emeric Deutsch_, May 10 2008