A163141 a(n) = 5*a(n-2) for n > 2; a(1) = 4, a(2) = 5.

4, 5, 20, 25, 100, 125, 500, 625, 2500, 3125, 12500, 15625, 62500, 78125, 312500, 390625, 1562500, 1953125, 7812500, 9765625, 39062500, 48828125, 195312500, 244140625, 976562500, 1220703125, 4882812500, 6103515625, 24414062500

Offset

1,1

Comments

Apparently the same as A133632 without initial 1.

Binomial transform is A163069, second binomial transform is A163070, third binomial transform is A163071, fourth binomial transform is A108404 without initial 1, fifth binomial transform is A163072.

Links

Table of n, a(n) for n=1..29.

Index entries for linear recurrences with constant coefficients, signature (0,5).

Formula

a(n) = (5-3*(-1)^n)*5^(1/4*(2*n-1+(-1)^n))/2.

G.f.: x*(4+5*x)/(1-5*x^2).

Mathematica

LinearRecurrence[{0, 5}, {4, 5}, 30] (* Harvey P. Dale, Dec 20 2021 *)

Prog

(Magma) [ n le 2 select n+3 else 5*Self(n-2): n in [1..29] ];
(PARI) Vec(x*(4+5*x)/(1-5*x^2) + O(x^30)) \\ Jinyuan Wang, Mar 23 2020

Crossrefs

Cf. A133632, A108404, A163069, A163070, A163071, A163072.

Sequence in context: A080610 A047175 A133632 * A182584 A358581 A240860

Adjacent sequences: A163138 A163139 A163140 * A163142 A163143 A163144

Keyword

nonn

Author

Klaus Brockhaus, Jul 21 2009

Status

approved