

A075556


Smallest prime p not occurring earlier such that p+n is a square, or 0 if no such p exists.


1



3, 2, 13, 5, 11, 19, 29, 17, 7, 71, 53, 37, 23, 67, 181, 0, 47, 31, 557, 61, 43, 59, 41, 97, 0, 199, 73, 197, 167, 139, 113, 89, 163, 191, 109, 0, 107, 83, 157, 401, 103, 79, 101, 317, 151, 179, 149, 241, 0, 239, 349, 173, 271, 307, 269, 233, 619, 383, 137, 229
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OFFSET

1,1


COMMENTS

a(n)=0 for square n.  Ralf Stephan, Mar 30 2003


LINKS

Table of n, a(n) for n=1..60.


PROG

(PARI) v=vector(1000000):for(n=1, 100, f=0:forprime(p=2, 1000000, if(!v[p]&&issquare(p+n), f=p:break)): if(f, print1(f", "):v[f]=1, print1("0, ")))


CROSSREFS

Cf. A075555, A075557.
Sequence in context: A198303 A093922 A075555 * A257568 A087357 A226062
Adjacent sequences: A075553 A075554 A075555 * A075557 A075558 A075559


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Sep 23 2002


EXTENSIONS

More terms from Ralf Stephan, Mar 30 2003


STATUS

approved



