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A108714
a(n)=minimal value of k, such that n^2+k^2 or (n^2+k^2)/2 are primes.
11
1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 1, 7, 2, 1, 1, 1, 2, 5, 1, 1, 4, 5, 3, 1, 1, 1, 2, 5, 1, 11, 4, 3, 2, 5, 1, 1, 2, 3, 1, 1, 4, 5, 3, 9, 1, 5, 2, 13, 1, 7, 1, 3, 3
OFFSET
1,7
COMMENTS
I am attempting to complete a proof that for every natural number n, there is at least one prime of the form n^2+k^2 or (n^2+k^2)/2 with 1<=k<=n.
EXAMPLE
a(3)=1 because (3^2+1)/2=5 (prime)
a(7)=2 ------> 7^2+2^2=53 (prime)
a(12)=7 -----> 12^2+7^2=193 (prime)
a(23)=3 -----> (23^2+3^2)/2=269 (prime)
a(48)=13 ----> 48^2+13^2=2473 (prime)
CROSSREFS
Sequence in context: A366292 A205104 A215561 * A135508 A030413 A139434
KEYWORD
nonn
AUTHOR
Robin Garcia, Jun 20 2005
STATUS
approved