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Fibonacci-like primefree sequences
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A083216: Fibonacci-like primefree sequence.
- { 20615674205555510, 3794765361567513, 24410439567123023, 28205204928690536, ... }
a (n) = a (n − 1) + a (n − 2), n ≥ 2 |
a (0) = 2 × 5 × 5623 × 366631232537 |
a (1) = 3 × 1264921787189171 |
And whereas the search for prime numbers seeks larger and larger primes, the search for primefree sequences seeks smaller initial terms. When in 1964, Ronald Graham (of Graham’s number fame) proved that this kind of sequence is possible, his example had initial terms with more than thirty digits each (in base 10). Donald Knuth found a 17-digit pair in 1990, and later that same year Herbert Wilf found this sequence with slightly smaller initial terms. The current record is a 12-digit pair found by John W. Nicol in 1999.