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A332884
a(n) = -n^2 + 21*n - 1.
0
19, 37, 53, 67, 79, 89, 97, 103, 107, 109, 109, 107, 103, 97, 89, 79, 67, 53, 37, 19, -1, -23, -47, -73, -101, -131, -163, -197, -233, -271, -311, -353, -397, -443, -491, -541, -593, -647, -703, -761, -821, -883, -947, -1013, -1081, -1151, -1223, -1297, -1373, -1451, -1531, -1613
OFFSET
1,1
COMMENTS
All the positive numbers of the form -(x^2 - 21*x + 1) are primes. Compare A335984.
REFERENCES
T. Özsoy, Visualization of Prime Numbers: Twin Prime Numbers, Ozsoy Triangle and Ozsoy Series, in A. Baki, B. Güven, and M. Güler, editors, Proc. 4th International Symposium of Turkish Computer and Mathematics Education, 26-Sep 28 2019, İzmir; pages 678-688.
FORMULA
G.f.: (x^2 + 20*x - 19)/(x - 1)^3. - Jinyuan Wang, Jul 08 2020
MATHEMATICA
Table[-n^2+21n-1, {n, 60}] (* or *) LinearRecurrence[{3, -3, 1}, {19, 37, 53}, 60] (* Harvey P. Dale, Mar 07 2023 *)
PROG
(PARI) a(n)=-n^2+21*n-1 \\ Charles R Greathouse IV, Oct 21 2022
CROSSREFS
Sequence in context: A245363 A109639 A225863 * A161705 A131600 A175546
KEYWORD
sign,easy
AUTHOR
Tamer Özsoy, Jul 02 2020
STATUS
approved