

A104199


Lower bound on a straddle prime pair.


0



3, 5, 7, 7, 7, 11, 13, 13, 13, 17, 19, 19, 19, 23, 23, 23, 23, 23, 29, 31, 31, 31, 31, 31, 37, 37, 37, 41, 43, 43, 43, 47, 47, 47, 47, 47, 53, 53, 53, 53, 53, 59, 61, 61, 61, 61, 61, 67, 67, 67, 71, 73, 73, 73, 73, 73, 79, 79, 79, 83, 83, 83, 83, 83, 89, 89, 89, 89, 89, 89, 89
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OFFSET

4,1


COMMENTS

Straddle primes that occur only once on either side of the composite number are lower and upper twin primes respectively.


LINKS

Table of n, a(n) for n=4..74.


FORMULA

Straddle primes are the nearest primes preceding and following a composite number n.


EXAMPLE

The first straddle prime pair is 3 and 5 which straddle the composite number 4.


PROG

(PARI) strad(n) = { my(y, pp, np); for(x=1, n, y=composite(x); pp=precprime(y); np=nextprime(y); print1(pp", ") ) }


CROSSREFS

Sequence in context: A297346 A211517 A254935 * A103470 A316852 A307120
Adjacent sequences: A104196 A104197 A104198 * A104200 A104201 A104202


KEYWORD

easy,nonn


AUTHOR

Cino Hilliard, Mar 13 2005


STATUS

approved



