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A108714
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a(n)=minimal value of k, such that n^2+k^2 or (n^2+k^2)/2 are primes.
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11
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,7
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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.
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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)
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CROSSREFS
| Sequence in context: A108756 A106178 A205104 * A135508 A030413 A139434
Adjacent sequences: A108711 A108712 A108713 * A108715 A108716 A108717
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KEYWORD
| nonn
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AUTHOR
| Robin Garcia (verob99(AT)teleline.es), Jun 20 2005
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