%I A109673
%S A109673 1,1,1,1,3,1,1,1,1,2,1,2,8,8,2,1,8,15,8,1,2,8,8,2,1,2,1,1,3,3,1,3,15,
%T A109673 24,15,3,3,24,60,60,24,3,1,15,60,93,60,15,1,3,24,60,60,24,3,3,15,
%U A109673 24,15,3,1,3,3,1,1,4,6,4,1,4,24,52,52,24,4,6,52,160,228,160,52,6,4,52
%N A109673 Hexagonal pyramid related to Prouhet-Tarry problem.
%C A109673 Entries of slices [n,n] in A109672, read by rows.
%C A109673 Greatest numbers in each slice (central numbers) form A002893 : 1, 3, 
               15, 93, 639, ...
%F A109673 Sum of terms in slice [n, n] = 3^(2n); example : 1+2+1+2+8+15+8+1+2+8+8+2+1+2+1 
               = 3^4 = 81 for the slice [2, 2].
%e A109673 Slice [0, 0]:
%e A109673 ... 1 ...
%e A109673 Slice [1,1]:
%e A109673 ... 1 1 ...
%e A109673 .. 1 3 1 ...
%e A109673 ... 1 1 ...
%e A109673 Slice [2,2]:
%e A109673 .... 1 2 1 ...
%e A109673 ... 2 8 8 2 ...
%e A109673 .. 1 8 15 8 1 ...
%e A109673 ... 2 8 8 2 ...
%e A109673 .... 1 2 1 ....
%e A109673 Slice [3,3]:
%e A109673 ...... 1 3 3 1 .....
%e A109673 .... 3 15 24 15 3 ...
%e A109673 ... 3 24 60 60 24 3 ...
%e A109673 .. 1 15 60 93 60 15 1 ...
%e A109673 ... 3 24 60 60 24 3 ...
%e A109673 .... 3 15 24 15 3 ....
%e A109673 ...... 1 3 3 1 ....
%Y A109673 Sequence in context: A109393 A030348 A143811 this_sequence A023591 A165661 
               A107711
%Y A109673 Adjacent sequences: A109670 A109671 A109672 this_sequence A109674 A109675 
               A109676
%K A109673 nonn,tabf,easy
%O A109673 0,5
%A A109673 Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Aug 07 2005