If i copy the above it works fine, clear your Memory (or restart mathematica) to be sure...
here is it with the original sequence:
ClearAll[xypos]
xypos[xs_List, y_] := MapThread[Text[#2, {#1, y}] &, {2 Range[Length[xs]] - Length[xs], xs}]
seq = {1, 2, 3, 4, 10, 19, 36, 69, 134};
seqs = Differences[seq, #] & /@ Range[0, Length[seq] - 1];
heights = Range[Length[seqs], 1, -1];
Graphics[MapThread[xypos, {seqs, heights}]]