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A017222
a(n) = (9*n + 5)^2.
5
25, 196, 529, 1024, 1681, 2500, 3481, 4624, 5929, 7396, 9025, 10816, 12769, 14884, 17161, 19600, 22201, 24964, 27889, 30976, 34225, 37636, 41209, 44944, 48841, 52900, 57121, 61504, 66049, 70756
OFFSET
0,1
FORMULA
a(n) = A017221(n)^2.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Harvey P. Dale, May 22 2012
G.f.: (25 + 121*x + 16*x^2)/(1-x)^3. - R. J. Mathar, Mar 20 2018
From G. C. Greubel, Dec 29 2022: (Start)
a(2*n+1) = 4*A017246(n).
a(n) = a(n-1) + 9*(18*n + 1).
E.g.f.: (25 + 171*x + 81*x^2)*exp(x). (End)
MATHEMATICA
(9Range[0, 30]+5)^2 (* or *) LinearRecurrence[{3, -3, 1}, {25, 196, 529}, 30] (* Harvey P. Dale, May 22 2012 *)
PROG
(Magma) [(9*n+5)^2: n in [0..35]]; // Vincenzo Librandi, Jul 24 2011
(PARI) a(n)=(9*n+5)^2 \\ Charles R Greathouse IV, Jun 17 2017
(SageMath) [(9*n+5)^2 for n in range(41)] # G. C. Greubel, Dec 29 2022
CROSSREFS
Sequences of the form (m*n+5)^2: A010864 (m=0), A000290 (m=1), A016754 (m=2), A016790 (m=3), A016814 (m=4), A016850 (m=5), A016970 (m=6), A017042 (m=7), A017126 (m=8), this sequence (m=9), A017330 (m=10), A017450 (m=11), A017582 (m=12).
Sequence in context: A243209 A146863 A101775 * A271535 A146738 A146722
KEYWORD
nonn,easy
STATUS
approved