OFFSET
1,1
LINKS
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
G.f.: 125*x / (1-x)^4.
a(n) = C(n+2,3)*5^3, n>=1.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4); a(1)=125, a(2)=500, a(3)=1250, a(4)=2500. - Harvey P. Dale, Oct 20 2012
From Amiram Eldar, Sep 01 2022: (Start)
Sum_{n>=1} 1/a(n) = 3/250.
Sum_{n>=1} (-1)^(n+1)/a(n) = 12*log(2)/125 - 3/50. (End)
MAPLE
seq(binomial(n+2, 3)*5^3, n=1..44);
MATHEMATICA
With[{c=5^3}, c*Binomial[Range[40]+2, 3]] (* Harvey P. Dale, Oct 20 2012 *)
LinearRecurrence[ {4, -6, 4, -1}, {125, 500, 1250, 2500}, 40] (* Harvey P. Dale, Oct 20 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Zerinvary Lajos, Aug 09 2008
EXTENSIONS
Offset corrected by Harvey P. Dale, Oct 20 2012
STATUS
approved