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 A110702 #13 Jul 23 2017 02:41:17 %S A110702 5,15,21,33,54,54,85,90,100,117,110,135,153,161,204,195,252,261,315, %T A110702 308,315,315,351,385,405,418,414,450,455,476,510,533,595,609,637,650, %U A110702 705,693,684,777,792,870,884,931,986,999,1071,1105,1121,1110,1125,1210,1230 %N A110702 Numbers S with two runsums (sum of positive integer runs) where the 2 runs are separated by a single number gap (b), i.e., S = a + (a+1) + ... + (b-1) = (b+1) + ... + c with a < b-1, b < c. %C A110702 The sums are the difference of two triangular numbers A000217. The sum series where the missing number is included is A110701. The numbers in the gap between the two runs are A094550. %H A110702 Ron Knott <a href="http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/runsums/">Runsums</a> %H A110702 T. Verhoeff, <a href="https://cs.uwaterloo.ca/journals/JIS/trapzoid.html">Rectangular and Trapezoidal Arrangements</a>, J. Integer Sequences, Vol. 2, 1999, #99.1.6. %e A110702 1+2+3+4+5 and 7+8 have a gap between them of (6). The sum of both is 15 so 15 is in the ordered series (as a(2)). %Y A110702 Cf. A001227, A094550, A110701, A110703. %K A110702 nonn %O A110702 1,1 %A A110702 _Ron Knott_, Aug 04 2005