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A168495
a(n) = 3^floor(n^2/3).
3
1, 1, 3, 27, 243, 6561, 531441, 43046721, 10460353203, 7625597484987, 5559060566555523, 12157665459056928801, 79766443076872509863361, 523347633027360537213511521, 10301051460877537453973547267843
OFFSET
0,3
COMMENTS
Hankel transform of A168494. Trivial Somos-4 sequence linked to elliptic curve y^2=1-10x+25x^2-12x^3.
LINKS
FORMULA
a(n) = 9*a(n-1)*a(n-3)/a(n-4).
MATHEMATICA
Table[3^Floor[n^2/3], {n, 0, 20}] (* G. C. Greubel, Sep 18 2018 *)
PROG
(Magma) [3^Floor(n^2/3): n in [0..15]]; // Vincenzo Librandi, Sep 15 2011
(PARI) vector(20, n, n--; 3^floor(n^2/3)) \\ G. C. Greubel, Sep 18 2018
CROSSREFS
Sequence in context: A013708 A102518 A361842 * A037763 A037651 A037770
KEYWORD
nonn,easy
AUTHOR
Paul Barry, Nov 27 2009
STATUS
approved