A162962 a(n) = 5*a(n-2) for n > 2; a(1) = 1, a(2) = 5.

1, 5, 5, 25, 25, 125, 125, 625, 625, 3125, 3125, 15625, 15625, 78125, 78125, 390625, 390625, 1953125, 1953125, 9765625, 9765625, 48828125, 48828125, 244140625, 244140625, 1220703125, 1220703125, 6103515625, 6103515625, 30517578125

Offset

1,2

Comments

Apparently a(n) = A074872(n+1), a(n) = A056451(n-1) for n > 1.

Binomial transform is A084057 without initial 1, second binomial transform is A048876, third binomial transform is A082762, fourth binomial transform is A162769, fifth binomial transform is A093145 without initial 0.

Links

Table of n, a(n) for n=1..30.

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

Formula

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

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

Mathematica

LinearRecurrence[{0, 5}, {1, 5}, 30] (* Harvey P. Dale, Mar 18 2023 *)

Prog

(Magma) [ n le 2 select 4*n-3 else 5*Self(n-2): n in [1..30] ];

Crossrefs

Cf. A000351 (powers of 5), A074872 (powers of 5 repeated), A056451 (5^floor((n+1)/2)), A084057, A048876, A082762, A162769, A093145.

Sequence in context: A227076 A223186 A071340 * A074872 A056451 A170834

Adjacent sequences: A162959 A162960 A162961 * A162963 A162964 A162965

Keyword

nonn,easy

Author

Klaus Brockhaus, Jul 19 2009

Status

approved