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A164532
a(n) = 6*a(n-2) for n > 2; a(1) = 1, a(2) = 4.
4
1, 4, 6, 24, 36, 144, 216, 864, 1296, 5184, 7776, 31104, 46656, 186624, 279936, 1119744, 1679616, 6718464, 10077696, 40310784, 60466176, 241864704, 362797056, 1451188224, 2176782336, 8707129344, 13060694016, 52242776064, 78364164096
OFFSET
1,2
COMMENTS
Interleaving of A000400 and A067411 without initial term 1.
Binomial transform is apparently A123011. Fourth binomial transform is A154235.
FORMULA
a(n) = (5 - (-1)^n)*6^(1/4*(2*n - 5 + (-1)^n)).
G.f.: x*(1+4*x)/(1-6*x^2).
a(n+3) = a(n+2)*a(n+1)/a(n). - Reinhard Zumkeller, Mar 04 2011
a(n) = ((1-(-1)^n)*sqrt(6)/2 + 2*(1+(-1)^n))*6^(n/2 -1). - G. C. Greubel, Jul 16 2021
MATHEMATICA
LinearRecurrence[{0, 6}, {1, 4}, 40] (* G. C. Greubel, Jul 16 2021 *)
PROG
(Magma) [ n le 2 select 3*n-2 else 6*Self(n-2): n in [1..29] ];
(Sage) [((1 - (-1)^n)*sqrt(6)/2 + 2*(1 + (-1)^n))*6^(n/2 -1) for n in (1..40)] # G. C. Greubel, Jul 16 2021
CROSSREFS
Cf. A000400 (powers of 6), A067411, A123011, A154235.
Sequence in context: A174197 A071224 A305381 * A098660 A363631 A122174
KEYWORD
nonn
AUTHOR
Klaus Brockhaus, Aug 15 2009
STATUS
approved