

A108393


a(n)=number of primes of the form p^2+k^2 with 2<=k<=floor(sqrt(2*p+1)) (less than (p+1)^2), for every p(n).


0



1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 2, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 2, 0, 1, 2, 1, 3, 2, 2, 0, 3, 1, 3, 2, 1, 3, 2, 5, 2, 2, 5, 2, 2, 3, 3, 1, 3, 2, 4, 3, 1, 1, 2, 1, 3, 4, 2, 2, 4, 1, 3, 2, 4, 3
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OFFSET

1,10


COMMENTS

Conjecture: 23,83,113 and 811 are the only primes with a 0 value in the sequence. There is always a prime of the form p^2+k^2 (1 mod 4) between p^2 and (p+1)^2 for every prime not 23,83,113 or 811.


LINKS

Table of n, a(n) for n=1..64.


EXAMPLE

a(5)=1 because p(5)=11 and very is only one value of k<=floor(sqrt(2*11+1))=4 for which p(5)^2+k^2 is prime: 11^2+4^2=137
a(27)=3 because p(27)=103 and 103^2+2^2=10613,103^2+10^2=10709,103^2+12^2=10753 are primes.


CROSSREFS

Cf. A108714.
Sequence in context: A325444 A058745 A275333 * A327342 A297828 A062245
Adjacent sequences: A108390 A108391 A108392 * A108394 A108395 A108396


KEYWORD

nonn


AUTHOR

Robin Garcia, Jul 02 2005


STATUS

approved



