

A105318


Starting prime for the smallest prime Pythagorean sequence for n triangles.


4




OFFSET

1,1


COMMENTS

Smallest prime p(0) such that the nchain governed by recurrence p(i+1)=(p(i)^2 + 1)/2 are all primes. Equivalently, least prime p(0) that generates a sequence of n 2prime triangles, where p(k) is the hypotenuse of the kth triangle and the leg of the (k+1)th triangle.


LINKS

Table of n, a(n) for n=1..8.
H. Dubner, Posting to Number Theory List
T. Forbes, Posting to Number Theory List
H. Dubner & T. Forbes, Prime Pythagorean Triangles
T. Forbes, Posting to Number Theory List
H. Dubner & T. Forbes, Journal of Integer Sequences, Vol. 4(2001) #01.2.3, Prime Pythagorean triangles
C. K. Caldwell, The Prime Glossary, Pythagorean triples


EXAMPLE

5 is a(1) because (5^2+1)/2 = 13 is prime, but (13^2+1)/2 = 85 is not.


CROSSREFS

Cf. A048161, A048270, A048295, A308635, A308636.
Sequence in context: A264738 A002208 A100653 * A304287 A121021 A237518
Adjacent sequences: A105315 A105316 A105317 * A105319 A105320 A105321


KEYWORD

hard,more,nonn


AUTHOR

Lekraj Beedassy, Apr 26 2005


EXTENSIONS

a(1) added by T. D. Noe, Jan 29 2011


STATUS

approved



