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A289356
Least number k such that n^2 + n + k is prime.
1
2, 1, 1, 1, 3, 1, 1, 3, 1, 7, 3, 5, 1, 9, 1, 1, 5, 1, 5, 3, 1, 1, 3, 5, 1, 3, 7, 1, 9, 7, 7, 5, 5, 1, 3, 17, 29, 3, 1, 7, 17, 1, 5, 9, 7, 11, 17, 11, 5, 9, 1, 5, 11, 17, 1, 3, 11, 1, 11, 1, 11, 11, 1, 17, 17, 7, 1, 5, 11, 1, 3, 1, 5, 5, 7, 1, 5, 1, 1, 3, 1, 11, 17, 5, 11, 11
OFFSET
0,1
COMMENTS
a(A002384(n)) = 1.
a(A027752(n)) = 3, for n > 2.
LINKS
FORMULA
a(n) = A013632(A002378(n)). - Robert Israel, Jul 05 2017
MAPLE
seq(nextprime(n^2+n)-(n^2+n), n=0..100); # Robert Israel, Jul 05 2017
MATHEMATICA
Table[k = 1; While[! PrimeQ[n^2 + n + k], k++]; k, {n, 0, 85}] (* Michael De Vlieger, Jul 04 2017 *)
PROG
(PARI) for(n=0, 85, k={my(k=1); while(!isprime(n^2+n+k), k++); k; }; print1(k", "))
CROSSREFS
Cf. A002378, A002384, A013632, A027752, A182047 (resulting primes).
Sequence in context: A047140 A047150 A280489 * A269977 A238710 A262905
KEYWORD
nonn
AUTHOR
Gionata Neri, Jul 03 2017
STATUS
approved