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 A059781 #16 Jul 02 2025 16:02:00 %S A059781 0,0,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,2,1,4,0,4,1,2,0,0,0,0,1,0,0,0,1,0, %T A059781 0,0,0,1,0,1,1,1,0,1,1,1,0,1,0,0,0,2,0,0,1,0,0,0,1,0,0,2,0,0,0,3,2,4, %U A059781 1,3,4,3,0,3,4,3,1,4,2,3,0,0,0,0,2,1,1,1,8,0,0,0,8,1,1,1,2,0,0,0,0,1,0,1,0 %N A059781 Triangle T(n,k) giving exponent of power of 2 dividing entry (n,k) of trinomial triangle A027907. %D A059781 Boris A. Bondarenko, Generalized Pascal Triangles and Pyramids (in Russian), FAN, Tashkent, 1990, ISBN 5-648-00738-8. %H A059781 Boris A. Bondarenko, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/pascal.html">Generalized Pascal Triangles and Pyramids</a>, English translation published by Fibonacci Association, Santa Clara Univ., Santa Clara, CA, 1993; see p. 117. %e A059781 0; 0,0,0; 0,1,0,1,0; ... %p A059781 with(numtheory): T := proc(i,j) option remember: if i >= 0 and j=0 then RETURN(1) fi: if i >= 0 and j=2*i then RETURN(1) fi: if i >= 1 and j=1 then RETURN(i) fi: if i >= 1 and j=2*i-1 then RETURN(i) fi: T(i-1,j-2)+T(i-1,j-1)+T(i-1,j): end: for i from 0 to 20 do for j from 0 to 2*i do if T(i,j) mod 2 = 1 then printf(`%d,`,0) else printf(`%d,`, ifactors(T(i,j))[2,1,2] ) fi: od:od: # _James Sellers_, Feb 22 2001 %K A059781 nonn,easy,tabf %O A059781 0,18 %A A059781 _N. J. A. Sloane_, Feb 22 2001 %E A059781 More terms from _James Sellers_, Feb 22 2001