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A010011
a(0) = 1, a(n) = 21*n^2 + 2 for n>0.
1
1, 23, 86, 191, 338, 527, 758, 1031, 1346, 1703, 2102, 2543, 3026, 3551, 4118, 4727, 5378, 6071, 6806, 7583, 8402, 9263, 10166, 11111, 12098, 13127, 14198, 15311, 16466, 17663, 18902, 20183, 21506, 22871, 24278, 25727, 27218, 28751, 30326, 31943, 33602, 35303
OFFSET
0,2
FORMULA
O.g.f.: 1-x*(23+17*x+2*x^2)/(-1+x)^3. - R. J. Mathar, Apr 12 2008
E.g.f.: (21*x*(x+1)+2)*e^x-1. - Gopinath A. R., Feb 13 2012
Sum_{n>=0} 1/a(n) = 3/4+sqrt(42)/84*Pi*coth( Pi*sqrt(42)/21) = 1.0738233857899... - R. J. Mathar, May 07 2024
a(n) = A069178(n)+A069178(n+1). - R. J. Mathar, May 07 2024
MAPLE
A010011:=n->`if`(n=0, 1, 21*n^2+2); seq(A010011(n), n=0..100); # Wesley Ivan Hurt, Nov 15 2013
MATHEMATICA
Join[{1}, 21 Range[41]^2 + 2] (* Bruno Berselli, Feb 06 2012 *)
Join[{1}, LinearRecurrence[{3, -3, 1}, {23, 86, 191}, 50]] (* Vincenzo Librandi, Aug 03 2015 *)
PROG
(Magma) [1] cat [21*n^2+2: n in [1..50]]; // Vincenzo Librandi, Aug 03 2015
CROSSREFS
Cf. A206399.
Sequence in context: A229449 A060456 A056580 * A172117 A217529 A284711
KEYWORD
nonn,easy
AUTHOR
STATUS
approved