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A162962 a(n) = 5*a(n-2) for n > 2; a(1) = 1, a(2) = 5. 1
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 (list; graph; refs; listen; history; text; internal format)
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).

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: A071340 A056451 A074872 * A170834 A154630 A245520

Adjacent sequences:  A162959 A162960 A162961 * A162963 A162964 A162965

KEYWORD

nonn,easy

AUTHOR

Klaus Brockhaus, Jul 19 2009

STATUS

approved

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Last modified September 21 19:57 EDT 2020. Contains 337273 sequences. (Running on oeis4.)