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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
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.
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
KEYWORD
nonn,easy
AUTHOR
Klaus Brockhaus, Jul 19 2009
STATUS
approved