A027470 a(n) = 225*(n-1)*(n-2)/2.

225, 675, 1350, 2250, 3375, 4725, 6300, 8100, 10125, 12375, 14850, 17550, 20475, 23625, 27000, 30600, 34425, 38475, 42750, 47250, 51975, 56925, 62100, 67500, 73125, 78975, 85050, 91350, 97875, 104625, 111600, 118800, 126225

Offset: 3

Author

Olivier Gérard

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 3..1000
• Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Crossrefs

Third diagonal of A027467.

Programs

Magma

[225*(n-1)*(n-2)/2: n in [3..50]]; // Vincenzo Librandi, Dec 29 2012

Maple

seq(225*binomial(n-1,2), n=3..50); # G. C. Greubel, May 14 2021

Mathematica

Table[225 (n-1) (n-2)/2, {n, 3, 50}] (* Vincenzo Librandi, Dec 29 2012 *)
LinearRecurrence[{3,-3,1},{225,675,1350},40] (* Harvey P. Dale, Feb 01 2013 *)

PARI

a(n)=225*(n-1)*(n-2)/2 \\ Charles R Greathouse IV, Jun 17 2017

Sage

[225*binomial(n-1,2) for n in (3..50)] # G. C. Greubel, May 14 2021

Formula

Numerators of sequence a[n,n-2] in (a[i,j])^4 where a[i,j] = binomial(i-1, j-1)/2^(i-1) if j<=i, 0 if j>i.

G.f.: 225*(1 - 3*x + 3*x^2)/(1 - x)^3. - Vincenzo Librandi, Dec 29 2012

a(3)=225, a(4)=675, a(5)=1350, a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - Harvey P. Dale, Feb 01 2013