Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #27 Jul 15 2018 13:53:30
%S 0,10,41,93,166,260,375,511,668,846,1045,1265,1506,1768,2051,2355,
%T 2680,3026,3393,3781,4190,4620,5071,5543,6036,6550,7085,7641,8218,
%U 8816,9435,10075,10736,11418,12121
%N a(n) = n*(21*n-1)/2.
%H G. C. Greubel, <a href="/A022278/b022278.txt">Table of n, a(n) for n = 0..5000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F a(n) = 21*n + a(n-1) - 11 for n > 0, a(0)=0. - _Vincenzo Librandi_, Aug 04 2010
%F G.f.: x*(10 + 11*x)/(1 - x)^3. - _R. J. Mathar_, Aug 04 2016
%F a(n) = A000217(11*n-1) - A000217(10*n-1). - _Bruno Berselli_, Oct 17 2016
%F E.g.f.: (x/2)*(21*x + 20)*exp(x). - _G. C. Greubel_, Aug 23 2017
%t Table[n (21 n - 1)/2, {n, 0, 100}] (* _Vladimir Joseph Stephan Orlovsky_, Mar 07 2011 *)
%o (PARI) a(n)=n*(21*n-1)/2 \\ _Charles R Greathouse IV_, Jun 16 2017
%Y Cf. A000217, A022278.
%Y Cf. similar sequences listed in A022288.
%K nonn,easy
%O 0,2
%A _N. J. A. Sloane_