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 A116096 #6 Jul 21 2021 22:45:37 %S A116096 21,30,902406,959721,6040059046,6242406405,9842410005,9900249006, %T A116096 15033519988494,17250863148969,22499666270469,27632040031654, %U A116096 34182546327286,37487353123861,52213551379230,74230108225630 %N A116096 Numbers k such that k concatenated with k-9 gives the product of two numbers which differ by 4. %e A116096 9900249006//9900248997 = 9949999499 * 9949999503, where // denotes concatenation. %Y A116096 Cf. A116095, A116097, A116104, A116227. %K A116096 nonn,base %O A116096 1,1 %A A116096 _Giovanni Resta_, Feb 06 2006