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 A109966 a(n) = 8^((n^2-n)/2). 3
 1, 1, 8, 512, 262144, 1073741824, 35184372088832, 9223372036854775808, 19342813113834066795298816, 324518553658426726783156020576256, 43556142965880123323311959751266331066368 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Sequence given by the Hankel transform (see A001906 for definition) of A082147 = {1, 1, 9, 89, 945, 10577, 123129, 1476841, ...}; example : det([1, 1, 9, 89; 1, 9, 89, 945; 9, 89, 945, 10577; 89, 945, 10577, 123129]) = 8^6 = 262144. Hankel transform of A059435 = [1, 2, 12, 88, 720, 6304, ...] . - Philippe Deléham, Sep 03 2006 The number of labeled graphs (with no self loops) such that at most three edges connect any vertex pair. - Geoffrey Critzer, Nov 10 2011 LINKS FORMULA a(n+1) is the determinant of n X n matrix M_(i, j) = binomial(8i, j). Hankel transform of A059435 = [1, 2, 12, 88, 720, 6304, ...] . - Philippe Deléham, Sep 03 2006 MATHEMATICA Table[2^(3*Binomial[n, 2]), {n, 0, 10}] (* Geoffrey Critzer, Nov 10 2011 *) PROG (PARI) a(n)=8^binomial(n, 2) \\ Charles R Greathouse IV, Jan 17 2012 (MAGMA) [2^(3*Binomial(n, 2)): n in [0..10]]; // G. C. Greubel, Feb 05 2018 CROSSREFS Cf. A006125, A047656, A053763, A053764, A109345, A109354, A109493. Sequence in context: A145259 A154025 A013713 * A139567 A035131 A067512 Adjacent sequences:  A109963 A109964 A109965 * A109967 A109968 A109969 KEYWORD nonn,easy,changed AUTHOR Philippe Deléham, Sep 01 2005 STATUS approved

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Last modified February 18 23:26 EST 2018. Contains 299330 sequences. (Running on oeis4.)