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 A195840 #13 Mar 30 2012 17:34:09 %S A195840 1,1,1,1,1,1,1,1,2,1,3,1,4,1,-1,4,1,-1,4,1,-1,4,1,-1,4,2,-1,5,3,-1,7, %T A195840 4,-1,10,4,-2,12,4,-3,13,4,-4,13,4,-4,13,5,-4,14,7,-4,-1,16,10,-4,-1, %U A195840 21,12,-5,-1,27,13,-7,-1,32,13,-10,-1,34 %N A195840 Triangle read by rows which arises from A195830, in the same way as A175003 arises from A195310. Column k starts at row A074377(k). %C A195840 The sum of terms of row n is equal to the leftmost term of row n+1. This sequence is related to the generalized decagonal numbers A074377, A195830 and A195850 in the same way as A175003 is related to the generalized pentagonal numbers A001318, A195310 and A000041. See comments in A195825. %e A195840 Written as a triangle: %e A195840 . 1; %e A195840 . 1; %e A195840 . 1; %e A195840 . 1; %e A195840 . 1; %e A195840 . 1; %e A195840 . 1, 1; %e A195840 . 2, 1; %e A195840 . 3, 1; %e A195840 . 4, 1, -1; %e A195840 . 4, 1, -1; %e A195840 . 4, 1, -1; %e A195840 . 4, 1, -1; %e A195840 . 4, 2, -1; %e A195840 . 5, 3, -1; %e A195840 . 7, 4, -1; %e A195840 . 10, 4, -2; %e A195840 . 12, 4, -3; %e A195840 . 13, 4, -4; %e A195840 . 13, 4, -4; %e A195840 . 13, 5, -4; %e A195840 . 14, 7, -4, -1; %e A195840 . 16, 10, -4, -1; %e A195840 . 21, 12, -5, -1; %e A195840 . 27, 13, -7, -1; %e A195840 . 32, 13, -10, -1; %e A195840 . 34, 13, -12, -1, 1; %Y A195840 Row sums give A195850. %Y A195840 Cf. A001082, A175003, A195828, A195836, A195837, A195838, A195839. %K A195840 sign,tabf %O A195840 1,9 %A A195840 _Omar E. Pol_, Sep 24 2011