A128988 a(n) = (n^3 - n^2)*5^n.

0, 100, 2250, 30000, 312500, 2812500, 22968750, 175000000, 1265625000, 8789062500, 59082031250, 386718750000, 2475585937500, 15551757812500, 96130371093750, 585937500000000, 3527832031250000, 21011352539062500

Offset: 1

Author

Mohammad K. Azarian, Apr 30 2007

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (20,-150,500,-625).

Crossrefs

Cf. A128796; A036289.

Programs

Magma

[(n^3-n^2)*5^n: n in [1..30]]; // Vincenzo Librandi, Oct 26 2011

Mathematica

Table[(n^3-n^2)5^n,{n,20}] (* or *) LinearRecurrence[{20,-150,500,-625},{0,100,2250,30000},20]

Formula

a(1)=0, a(2)=100, a(3)=2250, a(4)=30000, a(n)=20*a(n-1)- 150*a(n-2)+ 500*a(n-3)- 625*a(n-4). - Harvey P. Dale, Oct 25 2011

G.f.: (50*(5*x^2+2*x))/(5*x-1)^4. - Harvey P. Dale, Oct 25 2011

Extensions

Offset corrected by Mohammad K. Azarian, Nov 19 2008