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%I #20 Apr 25 2017 10:04:06
%S 1,2,1,2,4,2,1,2,4,8,4,2,1,2,4,8,16,8,4,2,1,2,4,8,16,32,16,8,4,2,1,2,
%T 4,8,16,32,64,32,16,8,4,2,1,2,4,8,16,32,64,128,64,32,16,8,4,2,1,2,4,8,
%U 16,32,64,128,256,128,64,32,16,8,4,2,1,2,4,8,16,32,64,128,256,512,256,128
%N Pyramidal sequence built with powers of 2.
%e Triangle begins:
%e 1
%e 2 1 2
%e 4 2 1 2 4
%e 8 4 2 1 2 4 8
%e 16 8 4 2 1 2 4 8 16
%e 32 16 8 4 2 1 2 4 8 16 32
%e 64 32 16 8 4 2 1 2 4 8 16 32 64
%e 128 64 32 16 8 4 2 1 2 4 8 16 32 64 128
%e 256 128 64 32 16 8 4 2 1 2 4 8 16 32 64 128 256
%e 512 256 128 64 32 16 8 4 2 1 2 4 8 16 32 64 128 256 512
%e 1024 512 256 128 64 32 16 8 4 2 1 2 4 8 16 32 64 128 256 512 1024
%e ... - _Philippe Deléham_, Mar 20 2013
%t pow2Pyram[row_] := Module[{st = 2^Range[0, row]}, Join[st, Reverse[Most[Rest[st]]]]]; Flatten[Array[pow2Pyram, 10]] (* _Harvey P. Dale_, May 09 2012 *)
%t Flatten[Table[Table[2^Abs[col], {col, -row, row}], {row, 0, 7}]] (* _Alonso del Arte_, Apr 15 2017 *)
%o (PARI) for(i=0,9,forstep(j=i,0,-1,print1(1<<j", "));for(j=1,i,print1(1<<j", "))) \\ _Charles R Greathouse IV_, Mar 20 2013
%Y Cf. A004738, A082693 (partial sums), A036563 (row sums).
%K nonn,tabf,easy
%O 1,2
%A _Benoit Cloitre_, Apr 12 2003
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