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A163141
a(n) = 5*a(n-2) for n > 2; a(1) = 4, a(2) = 5.
4
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.
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
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Jul 21 2009
STATUS
approved