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 A174225 #2 Mar 30 2012 18:57:11 %S A174225 2,3,4,5,9,8,7,25,27,6,11,49,125,10,32,13,121,343,14,243,64,17,169, %T A174225 1331,15,3125,729,12,19,289,2197,16,16807,15625,18,256,23,361,4913,21, %U A174225 161051,117649,20,6561,512,29,529,6859,22 %N A174225 Array: row n consists of the positive integers x for which there are exactly n positive integers y such that x+y divides x*y. %C A174225 Many properties of the array follow easily from Comments at A063647: %C A174225 1. Every positive integer except 1 occurs, exactly once. %C A174225 2. Row 1 consists of the primes. %C A174225 3. Row k includes p^k for all primes p, for k>=1. %C A174225 4. Row 4 includes all products of two distinct primes. %C A174225 5. Column 1 consists of even numbers. %e A174225 Corner of the array: %e A174225 2....3....5....7....11....13.... %e A174225 4....9....25...49...121...169... %e A174225 8....27...125..343..1331..2197.. %e A174225 6....10...14...15...16....21.... %e A174225 6 is in row 4 because there are 4 numbers y for which %e A174225 6+y divides 6*y; they are 3,6,12,30. %Y A174225 Cf. A063647. %K A174225 nonn,tabl %O A174225 1,1 %A A174225 _Clark Kimberling_, Mar 12 2010