Numero di Skewes: differenze tra le versioni
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Riga 28:
:7 × 10<sup>370</sup>.
Una approssimazione migliore era 1.39822 × 10<sup>316</sup> scoperta da Bays e Hudson (2000). Il miglior valore per il primo attraversamento di zero è ora 1.397162914 × 10<sup>316</sup> ([[Patrick Demichel|Demichel]] 2005). Questo è, con un [[intervallo di confidenza]] molto elevato, il primo caso per cui si verifica Li(''x'') < π(''x'') [http://www.
Skewes' task was to make Littlewood's existence proof [[effective results in number theory|effective]]: exhibiting some concrete upper bound for the first sign change. According to [[George Kreisel]], this was at the time not considered obvious even in principle. The approach called ''[[unwinding]]'' in [[proof theory]] looks directly at proofs and their structure to produce bounds. The other way, more often seen in practice in number theory, changes proof structure enough so that absolute constants can be made more explicit.
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