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 A134673 #24 Apr 03 2022 17:30:44 %S A134673 1,0,2,0,0,3,1,-1,0,4,0,0,0,0,5,2,-1,-2,0,0,6,0,0,0,0,0,0,7,1,1,0,-3, %T A134673 0,0,0,8,1,0,-2,0,0,0,0,0,9,2,-1,0,0,-4,0,0,0,0,10,0,0,0,0,0,0,0,0,0, %U A134673 0,11,1,3,1,-3,0,-5,0,0,0,0,0,12,0,0,0,0,0,0,0,0,0,0,0,0,13,2,-1 %N A134673 A051731 + A127448 - I where I is the Identity matrix (A023531). %C A134673 Row sums = A073757: (1, 2, 3, 4, 5, 5, 7, 7, 8, 7, ...). %F A134673 a(n) = A051731(n) + A127448(n) - A023531(n). %F A134673 T(n,k) = k*A008683(n/k) + 1 if k divides n and k < n, T(n,k)=n for k=n, and T(n,k)=0 otherwise. - _Max Alekseyev_, Jan 07 2015 %e A134673 First few rows of the triangle: %e A134673 1; %e A134673 0, 2; %e A134673 0, 0, 3; %e A134673 1, -1, 0, 4; %e A134673 0, 0, 0, 0, 5; %e A134673 2, -1, -2, 0, 0, 6; %e A134673 0, 0, 0, 0, 0, 0, 7; %e A134673 1, 1, 0, -3, 0, 0, 0, 8; %e A134673 ... [Typo corrected by _N. J. A. Sloane_, May 22 2010] %o A134673 (PARI) A134673(n,k) = if(n%k,0,if(k==n,n,k*moebius(n/k)+1)); /* _Max Alekseyev_, Jan 07 2015 */ %Y A134673 Cf. A127448, A073757, A051731. %K A134673 tabl,sign %O A134673 1,3 %A A134673 _Gary W. Adamson_, Nov 05 2007 %E A134673 More terms from _Max Alekseyev_, Apr 03 2022