Intended for: July 19, 2012
Timetable
- First draft entered by Alonso del Arte on April 29, 2011 based on a verbatim write-up from November 10, 2011. ✓
- Draft reviewed by Alonso del Arte on July 15, 2011 ✓
- Draft approved by Daniel Forgues on June 21, 2011 ✓
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A059999:
| n 5 − n 4 + n 3 − n 2 + n − 14, n ≥ 1 |
.
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{ 2, 3, 5, 7, 11, 42, 168, ... }
If instead of the first seven terms I had given the first five, you might have guessed that the next five terms are 13, 17, 19, 23, 29. That is, unless you know by heart that the sequence of prime numbers has a much lower A-number in the OEIS, namely A000040. Rainer Rosenthal “deliberately contrived” this sequence “to begin with [the] first five primes” in order to illustrate the “absurdity of many ‘guess the next term’ puzzles.”
I think this sequence also makes two other important points. First, it shows the futility of searching for an arithmetic formula that will give the prime numbers in order, since such a level of complication is required for a formula that gives just the first five primes in order. Second, it shows the usefulness of the OEIS in finding formulae when one only knows a few terms of the sequence.
