A081553 Sum of n-th row of A081551.

1, 21, 303, 4006, 50010, 600015, 7000021, 80000028, 900000036, 10000000045, 110000000055, 1200000000066, 13000000000078, 140000000000091, 1500000000000105, 16000000000000120, 170000000000000136, 1800000000000000153, 19000000000000000171, 200000000000000000190, 2100000000000000000210, 22000000000000000000231

Offset: 1

Author

Amarnath Murthy, Apr 01 2003

Keywords

• base
• easy
• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..500
• Index entries for linear recurrences with constant coefficients, signature (23,-163,361,-320,100).

Crossrefs

Cf. A081551, A081552.

Cf. A126431, A161680.

Programs

Mathematica

Table[n*10^(n-1) +n(n-1)/2, {n,40}] (* G. C. Greubel, May 27 2021 *)

Sage

[n*10^(n-1) +binomial(n,2) for n in (1..40)] # G. C. Greubel, May 27 2021

Formula

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

From G. C. Greubel, May 27 2021: (Start)

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

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

Extensions

Terms a(13) onward added by G. C. Greubel, May 27 2021