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 A097994 #3 Mar 30 2012 18:37:44
%S A097994 1,3,0,3,3,0,6,6,0,1,3,15,3,3,0,9,21,6,12,0,0,3,34,21,25,3,0,0,10,45,
%T A097994 36,54,15,0,0,0,6,54,72,108,36,6,0,0,0,9,84,102,172,117,15,0,1,0,0,3,
%U A097994 84,174,306,228,54,7,3,0,0,0,18,114,225,483,447,162,18,12,0,0,0,0,3,114
%N A097994 T(n,k) counts plane partitions of n that can be 'extended' in (k+2) ways to a plane partition of n+1 by adding 1 element to it. Equivalently, it counts how many partitions of n have (k+2) different partitions of n+1 just covering it.
%C A097994 The first column starts a t k=3 since all plane partitions can be extended in at least 3 ways. Row sums are A000219 by definition. Sum T(n,k) (k+2) =A090984.
%e A097994 T(4,4)=1 because {{2,1},{1}} is the only plane partition of 4 that can be extended in 4+2 = 6 ways to a plane partition of 5.
%t A097994 (* functions 'planepartitions' and 'coversplaneQ', see A096574 *) Table[Frequencies[Count[planepartitions[n+1], q_/; coversplaneQ[q, # ]]&/@ planepartitions[n]], {n, 1, 16}]
%Y A097994 Cf. A000219, A090984.
%K A097994 hard,nonn,tabl
%O A097994 1,2
%A A097994 _Wouter Meeussen_, Sep 07 2004