It says “4×10^17 is a number so mind bogglingly big it would take about 45 trillion years to write out, writing 1 digit every second.” Not so, I can easily write it in this comment field: 400,000,000,000,000,000. The number of digits can be found by finding the power of 10 (in this case 17), and adding 1 (assuming the coefficient is less than 10).

Perhaps what was meant was that if every such number in the sequence of even numbers was written, it would take about 45 trillion years. Even then, that’s a bit too large. Calculating the number of total digits, one would have to write about 33,086,419,753,086,420 digits (A014925(16) * 5 * 4). This however would only take about 33,086,419,753,086,420 / (60 sec * 60 min * 24 hrs * 365.2425 yrs) ≈ 1,048,466,904 years to write the digits, at a rate of 1 digit per second. So in truth, it would only take about 1 billion years, which is 4 orders of magnitude difference from the 45 trillion estimate. This seems to suggest that either the original calculation used some unorthodox rounding, or that it was calculating something else entirely.

Link to the relevant OEIS sequence: http://oeis.org/A014925

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