A081553 - OEIS

%I #7 May 29 2021 20:05:10

%S 1,21,303,4006,50010,600015,7000021,80000028,900000036,10000000045,

%T 110000000055,1200000000066,13000000000078,140000000000091,

%U 1500000000000105,16000000000000120,170000000000000136,1800000000000000153,19000000000000000171,200000000000000000190,2100000000000000000210,22000000000000000000231

%N Sum of n-th row of A081551.

%H G. C. Greubel, <a href="/A081553/b081553.txt">Table of n, a(n) for n = 1..500</a>

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (23,-163,361,-320,100).

%F a(n) = n*10^(n-1) + n*(n-1)/2.

%F From _G. C. Greubel_, May 27 2021: (Start)

%F G.f.: x*(1 -2*x -17*x^2 +99*x^3)/((1-x)^3 * (1-10*x)^2).

%F E.g.f.: (1/2)*x*( x*exp(x) + 2*exp(10*x) ). (End)

%t Table[n*10^(n-1) +n(n-1)/2, {n,40}] (* _G. C. Greubel_, May 27 2021 *)

%o (Sage) [n*10^(n-1) +binomial(n,2) for n in (1..40)] # _G. C. Greubel_, May 27 2021

%Y Cf. A081551, A081552.

%Y Cf. A126431, A161680.

%K base,easy,nonn

%O 1,2

%A _Amarnath Murthy_, Apr 01 2003

%E Terms a(13) onward added by _G. C. Greubel_, May 27 2021