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 A081757 #9 May 24 2013 21:29:07 %S A081757 0,0,0,0,1,1,1,1,1,1,2,1,2,1,2,1,2,1,3,1,2,2,2,1,3,1,2,2,3,1,3,1,3,2, %T A081757 2,1,4,1,2,2,4,1,3,1,3,3,2,1,4,1,3,2,3,1,4,2,3,2,2,1,6,1,2,2,3,2,4,1, %U A081757 3,2,4,1,5,1,2,3,3,2,4,1,4,2,2,1,6,2,2,2,4,1,5,2,3,2,2,2,6,1,3,2,4,1,4,1,4 %N A081757 Number of ways to write n as i*j+i-j, 0<i<j. %H A081757 Reinhard Zumkeller, <a href="/A081757/b081757.txt">Table of n, a(n) for n = 1..1000</a> %F A081757 G.f.: Sum(x^(n^2+3*n)/(1-x^n),n = 1 .. infinity). - _Vladeta Jovovic_, May 13 2008 %e A081757 n=25 = 2*23+2-23 = 3*11+3-11 = 4*7+4-7, therefore a(25)=3. %o A081757 (Haskell) %o A081757 a081757 n = length [() | j <- [2..n], i <- [1..j-1], i * j + i - j == n] %o A081757 -- _Reinhard Zumkeller_, May 24 2013 %Y A081757 Cf. A072670. %K A081757 nonn %O A081757 1,11 %A A081757 _Reinhard Zumkeller_, Apr 08 2003