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 A300306 #9 Mar 09 2018 17:52:05
%S A300306 1,4,7,10,14,18,22,26,31,35,40,45,49,54,59,64,69,74,79,85,90,95,101,
%T A300306 106,112,117,123,128,134,139,145,151,157,162,168,174,180,186,192,198,
%U A300306 204,210,216,222,228,234,240,246,252,258,264,271,277,283,289,296,302,308,315,321,327,334
%N A300306 Expected rounded number of draws until two persons simultaneously drawing cards with replacement from two separate decks of n cards, both obtain complete collections.
%C A300306 Coupon collector's problem for two persons.
%F A300306 a(n) = round(1 - Sum_{j=0..n} Sum_{k=0..n} ( (-1)^(2*n-j-k) * binomial(n,j) * binomial(n,k) * j * k / (n^2-j*k) )) excluding term with j=k=n in summation.
%e A300306 a(1)=1, a(2)=round(11/3)=3, a(3)=round(1909/280)=7, a(4)=round(4687/455)=10, a(5)=round(7517050763/535422888)=14.
%Y A300306 Cf. A300305 (diagonal in triangle).
%K A300306 nonn
%O A300306 1,2
%A A300306 _Hugo Pfoertner_, Mar 07 2018