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%I #29 Sep 08 2022 08:45:00
%S 20,70,120,170,220,270,320,370,420,470,520,570,620,670,720,770,820,
%T 870,920,970,1020,1070,1120,1170,1220,1270,1320,1370,1420,1470,1520,
%U 1570,1620,1670,1720,1770,1820,1870,1920,1970,2020,2070,2120,2170,2220,2270
%N Sum of even numbers in range 10*n to 10*n+9.
%H Vincenzo Librandi, <a href="/A053741/b053741.txt">Table of n, a(n) for n = 0..10000</a>
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F a(n) = 50*n + 20.
%F From _Colin Barker_, Jun 27 2012: (Start)
%F a(n) = 2*a(n-1) - a(n-2).
%F G.f.: 10*(2+3*x)/(1-x)^2. (End)
%F E.g.f.: 10*(2+5*x)*exp(x). - _G. C. Greubel_, Sep 06 2019
%e 20 is sum of 0, 2, 4, 6, 8;
%e 70 is sum of 10, 12, 14, 16, 18;
%e 120 is sum of 20, 22, 24, 26, 28; etc.
%p seq(10*(2+5*n), n=0..50); # _G. C. Greubel_, Sep 06 2019
%t 50Range[50]-30 (* _Harvey P. Dale_, Mar 06 2011 *)
%o (Magma) [20+50*n: n in [0..50]]; // _Vincenzo Librandi_, Aug 12 2011
%o (PARI) vector(50, n, 10*(5*n-3)) \\ _G. C. Greubel_, Sep 06 2019
%o (Sage) [10*(2+5*n) for n in (0..50)] # _G. C. Greubel_, Sep 06 2019
%o (GAP) List([0..50], n-> 10*(2+5*n)); # _G. C. Greubel_, Sep 06 2019
%Y Cf. A053742, A053743.
%K nonn,easy
%O 0,1
%A _Odimar Fabeny_, Feb 13 2000
%E More terms from _James A. Sellers_, Feb 22 2000
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