A215146 - OEIS

%I #13 Sep 08 2022 08:46:03

%S 1,22,43,64,85,106,127,148,169,190,211,232,253,274,295,316,337,358,

%T 379,400,421,442,463,484,505,526,547,568,589,610,631,652,673,694,715,

%U 736,757,778,799,820,841,862,883,904,925,946,967,988

%N a(n) = 21*n + 1.

%H Jeremy Gardiner, <a href="/A215146/b215146.txt">Table of n, a(n) for n = 0..999</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).

%F From _G. C. Greubel_, Apr 19 2018: (Start)

%F a(n) = 2*a(n-1) - a(n-2).

%F G.f.: (1+20*x)/(1-x)^2.

%F E.g.f.: (21*x + 1)*exp(x). (End)

%t Range[1, 1000, 21]

%t LinearRecurrence[{2,-1}, {1,22}, 50] (* _G. C. Greubel_, Apr 19 2018 *)

%o (PARI) for(n=0, 50, print1(21*n + 1, ", ")) \\ _G. C. Greubel_, Apr 19 2018

%o (Magma) I:=[1,22]; [n le 2 select I[n] else 2*Self(n-1) - Self(n-2): n in [1..30]]; // _G. C. Greubel_, Apr 19 2018

%Y Cf. A124198, A161709.

%K nonn,easy

%O 0,2

%A _Jeremy Gardiner_, Aug 04 2012