Kolmogorov complexity captures your example. Kolmogorov complexity is the length of the shortest computer code that encodes a sequence. So the digits of Pi has

Kolmogorov complexity captures your example. Kolmogorov complexity is the length of the shortest computer code that encodes a sequence. So the digits of Pi has a low computational complexity, because short programs exist that iteratively estimate PI. Random sequences have a high Kolmogorov complexity as their are no ways of generating the data. Kolmogorov complexity measures the compressibility of a sequence. Its related to the information content, and is NP-Hard to compute! The measure that takes into account the time to compute a sequence is the newer measure called "logical depth", but I only heard about that last week. The sequence of Ramsey numbers would have be very logically deep. A short program exists, but it takes forever to computer. The logical depth captures the amount of time you are saved by having the sequence precomputed.