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A126906 Smallest k such that 1 + k^(2*n+1) + Sum_{j=1..n} k^(2*j) is prime. 1
1, 2, 1, 2, 1, 10, 17, 2, 1, 2, 1, 94, 122, 22, 1, 80, 1, 4, 6, 2, 1, 242, 3, 6, 5, 80, 1, 12, 1, 82, 96, 2, 7, 188, 1, 136, 69, 158, 1, 2, 1, 954, 50, 118, 1, 570, 14, 90, 45, 6, 1, 228, 38, 4, 6, 22, 1, 12, 1, 580, 86, 336, 24, 768, 1, 1170, 408, 340, 1, 896 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
1 is a term if and only if number of terms in polynomial is prime.
LINKS
MATHEMATICA
a[n_]: = Module[{k = 1}, While[!PrimeQ[1 + k^(2*n+1) + Sum[k^(2*j), {j, 1, n}]], k++]; k]; Array[a, 30] (* Amiram Eldar, Mar 13 2020 *)
PROG
(PARI) a(n) = my(k = 1); while(! isprime(1 + k^(2*n+1) + sum(j=1, n, k^(2*j))), k++); k; \\ Michel Marcus, Mar 13 2020
CROSSREFS
Sequence in context: A071560 A248516 A097749 * A179508 A134304 A211096
KEYWORD
nonn
AUTHOR
Artur Jasinski, Dec 31 2006
EXTENSIONS
More terms from Amiram Eldar, Mar 13 2020
STATUS
approved

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Last modified June 14 19:03 EDT 2024. Contains 373401 sequences. (Running on oeis4.)