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 A156837 #7 Jun 02 2025 01:23:36 %S A156837 1,2,1,2,0,1,3,3,0,1,2,0,0,0,1,4,4,4,0,0,1,2,0,0,0,0,0,1,4,7,0,5,0,0, %T A156837 0,1,3,0,7,0,0,0,0,0,1,4,6,0,0,6,0,0,0,0,1,2,0,0,0,0,0,0,0,0,0,1,6,12, %U A156837 14,11,0,7,0,0,0,0,0,1 %N A156837 Triangle read by rows, A051731 * A156348. %C A156837 Left border: A000005(n). %C A156837 Row sums = 3 iff n-th row is prime. %F A156837 Triangle read by rows, A051731 * A156348 = inverse Mobius transform of A156348 %e A156837 First few rows of the triangle = %e A156837 1; %e A156837 2, 1; %e A156837 2, 0, 1; %e A156837 3, 3, 0, 1; %e A156837 2, 0, 0, 0, 1; %e A156837 4, 4, 4, 0, 0, 1; %e A156837 2, 0, 0, 0, 0, 0, 1; %e A156837 4, 7, 0, 5, 0, 0, 0, 1; %e A156837 3, 0, 7, 0, 0, 0, 0, 0, 1; %e A156837 4, 6, 0, 0, 6, 0, 0, 0, 0, 1; %e A156837 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1; %e A156837 6, 12, 14, 11, 0, 7, 0, 0, 0, 0, 0, 1; %e A156837 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1; %e A156837 4, 8, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 1; %e A156837 ... %p A156837 A156837 := proc(n,k) %p A156837 add(A051731(n,j)*A156348(j,k),j=k..n) ; %p A156837 end proc: # _R. J. Mathar_, Mar 03 2013 %Y A156837 Cf. A156348, A051731, A000005, A156838 (row sums). %K A156837 nonn,tabl,easy %O A156837 1,2 %A A156837 _Gary W. Adamson_ & _Mats Granvik_, Feb 16 2009