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

Author

Klaus Brockhaus, Jul 21 2009

Keywords

• nonn

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

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

Crossrefs

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

Programs

Magma

[ n le 2 select n+3 else 5*Self(n-2): n in [1..29] ];

Mathematica

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

PARI

Vec(x*(4+5*x)/(1-5*x^2) + O(x^30)) \\ Jinyuan Wang, Mar 23 2020

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).