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 A116185 #9 Jul 19 2021 19:54:26 %S A116185 150,186,324,376,666,2046,3000,82650,100384,466716,1322316,4049584, %T A116185 67820074,110003884,135734074,156502836,196043286,213017754,238849000, %U A116185 261405396,289940826,310507774,365294050,398891964,446667216 %N A116185 Numbers k such that k concatenated with k+4 gives the product of two numbers which differ by 3. %C A116185 Also numbers k such that k concatenated with k+6 gives the product of two numbers which differ by 1. %p A116185 cc:=proc(x,y) local s: s:=proc(m) nops(convert(m,base,10)) end: x*10^s(y)+y: end: a:=proc(n) if type(sqrt(9+4*cc(n,n+4)),integer) then n else fi end: seq(a(n),n=1..500000); # very slow; cc yields the concatenation of x and y; - _Emeric Deutsch_, May 05 2007 %Y A116185 Cf. A116112, A115428, A115429, A116316, A116199, A116172, A116329. %K A116185 nonn,base %O A116185 1,1 %A A116185 _Giovanni Resta_, Feb 06 2006 %E A116185 Edited by _N. J. A. Sloane_, Apr 14 2007