id:A115766 - OEIS Search Results

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Distance from the n-th prime to the nearest semiprime.

+0
2

2, 1, 1, 1, 1, 1, 2, 2, 1, 3, 2, 1, 2, 3, 1, 2, 1, 1, 2, 2, 1, 2, 1, 2, 2, 5, 3, 1, 2, 2, 2, 2, 3, 2, 3, 4, 1, 2, 1, 4, 1, 2, 3, 1, 3, 2, 2, 2, 1, 3, 2, 2, 4, 2, 2, 1, 2, 3, 1, 3, 4, 2, 2, 2, 1, 2, 2, 2, 1, 3, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 1, 4, 4, 2, 2, 2, 1, 3, 3, 1, 1, 2, 2, 2, 1, 2, 2, 3, 1, 2, 2, 1, 3, 2 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`This is a very slow-growing function. For the first 10^8 primes, the largest value is 45, which occurs for the prime 981270947.`
	EXAMPLE	`a(10)=3 because 29 is the 10th prime and the nearest semiprime is 26.`
	MATHEMATICA	`SemiPrimeQ[n_] := (2==Plus@@(Transpose[FactorInteger[n]][[2]])); Join[{2}, Table[p=Prime[i]; j=1; While[ !SemiPrimeQ[p+j] && !SemiPrimeQ[p-j], j++ ]; j, {i, 2, 150}]]`
	CROSSREFS	`Cf. A001358 (semiprimes).` `Sequence in context: A083382 A025900 A118383 this_sequence A108339 A138559 A073454` `Adjacent sequences: A115763 A115764 A115765 this_sequence A115767 A115768 A115769`
	KEYWORD	`easy,nonn`
	AUTHOR	`T. D. Noe (noe(AT)sspectra.com), Jan 30 2006`

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Last modified November 18 20:14 EST 2008. Contains 147244 sequences.

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