Geometric series

say ~(1, 2, 4 ... 1000)
# 1 2 4 8 16 32 64 128 256 512

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say ~(2, 6, 18 ... 1000)
# 2 6 18 54 162 486

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say ~(1, .1, .01 ... .0000001)
# 1 0.1 0.01 0.001 0.0001 1e-05 1e-06

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say ~(1, -1, 1 ... *).[^10]
# 1 -1 1 -1 1 -1 1 -1 1 -1