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A016922
a(n) = (6*n+1)^2.
25
1, 49, 169, 361, 625, 961, 1369, 1849, 2401, 3025, 3721, 4489, 5329, 6241, 7225, 8281, 9409, 10609, 11881, 13225, 14641, 16129, 17689, 19321, 21025, 22801, 24649, 26569, 28561, 30625, 32761, 34969, 37249, 39601, 42025, 44521, 47089, 49729, 52441, 55225
OFFSET
0,2
COMMENTS
Except for 2, exponents e such that x^e-x+1 is reducible.
FORMULA
G.f.: ( 1+46*x+25*x^2 ) / (1-x)^3. - R. J. Mathar, Mar 10 2011
a(n) = A016921(n)^2 = A000290(A016921(n)). - Wesley Ivan Hurt, Dec 06 2013
a(n) = 24*A005449(n)+1. - Jean-Bernard François, Oct 12 2014
a(n) = 3*a(n-1)-3*a(n-2)+a(n-3). - Wesley Ivan Hurt, Oct 13 2014
Sum_{n>=0} 1/a(n) = A086727. - Amiram Eldar, Nov 16 2020
MAPLE
A016922:=n->(6*n+1)^2; seq(A016922(n), n=0..100); # Wesley Ivan Hurt, Dec 06 2013
MATHEMATICA
Table[(6n+1)^2, {n, 0, 100}] (* or *)
CoefficientList[Series[(1 + 46*x + 25*x^2)/(1 - x)^3, {x, 0, 30}], x] (* Wesley Ivan Hurt, Oct 13 2014 *)
LinearRecurrence[{3, -3, 1}, {1, 49, 169}, 50] (* Harvey P. Dale, Feb 17 2023 *)
PROG
(Magma) [(6*n+1)^2: n in [0..60]]; // Vincenzo Librandi, May 04 2011
(PARI) a(n)=(6*n+1)^2 \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
Cf. A000290, A005449, A086727, A016778 (bisection), A016921.
Sequence in context: A254624 A256074 A369565 * A277793 A147608 A258060
KEYWORD
nonn,easy
AUTHOR
STATUS
approved