A164640 - OEIS

A164640

a(n) = 8*a(n-2) for n > 2; a(1) = 1, a(2) = 6.

1, 6, 8, 48, 64, 384, 512, 3072, 4096, 24576, 32768, 196608, 262144, 1572864, 2097152, 12582912, 16777216, 100663296, 134217728, 805306368, 1073741824, 6442450944, 8589934592, 51539607552, 68719476736, 412316860416

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OFFSET

1,2

COMMENTS

Interleaving of A001018 and A083233 without initial term 1.

Binomial transform is A164544. Third binomial transform is A038761.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..300

Index entries for linear recurrences with constant coefficients, signature (0, 8).

FORMULA

a(n) = (7-(-1)^n)*2^(1/4*(6*n -15+3*(-1)^n)).

G.f.: x*(1+6*x)/(1-8*x^2).

MATHEMATICA

LinearRecurrence[{0, 8}, {1, 6}, 40] (* Harvey P. Dale, Nov 06 2013 *)

PROG

(Magma) [ n le 2 select 5*n-4 else 8*Self(n-2): n in [1..26] ];

(PARI) a(n)=(7-(-1)^n)*2^(1/4*(6*n-15+3*(-1)^n)) \\ Charles R Greathouse IV, Oct 07 2015

CROSSREFS

Cf. A001018 (powers of 8), A083233 ((3*8^n+(0)^n)/4), A164544, A038761.

Sequence in context: A261063 A000380 A154153 * A223852 A227167 A192158

Adjacent sequences: A164637 A164638 A164639 * A164641 A164642 A164643

KEYWORD

nonn,easy

AUTHOR

Klaus Brockhaus, Aug 20 2009

EXTENSIONS

G.f. corrected by Klaus Brockhaus, Sep 18 2009

STATUS

approved