A127849 a(n) = 5^C(n,2)*(5^n-1)/4.

0, 1, 30, 3875, 2437500, 7626953125, 119201660156250, 9313106536865234375, 3637969493865966796875000, 7105423719622194766998291015625, 69388931933644926175475120544433593750

Offset: 0

Author

Paul Barry, Feb 02 2007

Keywords

• easy
• nonn

Comments

-a(n) is the Hankel transform of A127848, the series reversion of x/(1+6*x+5*x^2). Note that (5^n-1)/4 has g.f. x/(1-6*x+5*x^2).

(-1)^n*a(n) is the Hankel transform of the series reversion of x*(1+4*x)/(1+2*x-3*x^2). - Paul Barry, Jul 12 2008

Crossrefs

Cf. A127848.

Programs

Mathematica

Table[5^Binomial[n,2] (5^n-1)/4,{n,0,20}] (* Harvey P. Dale, Dec 31 2022 *)