|
|
A105318
|
|
Starting prime for the smallest prime Pythagorean sequence for n triangles.
|
|
4
|
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Smallest prime p(0) such that the n-chain 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 2-prime triangles, where p(k) is the hypotenuse of the k-th triangle and the leg of the (k+1)-th triangle.
|
|
LINKS
|
|
|
EXAMPLE
|
5 is a(1) because (5^2+1)/2 = 13 is prime, but (13^2+1)/2 = 85 is not.
|
|
CROSSREFS
|
|
|
KEYWORD
|
hard,more,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|