OFFSET
1,1
COMMENTS
Explicit formula and asymptotic are given by Chang and Chen (2011).
a(7) contains 134 decimal digits.
LINKS
S.-C. Chang, L.-C. Chen. Hamiltonian walks on the Sierpinski gasket, J. Math. Phys. 52 (2011), 023301. doi:10.1063/1.3545358. See also, arXiv:0909.5541 [cond-mat.stat-mech], 2009.
Eric Weisstein's World of Mathematics, Hamiltonian Path
Eric Weisstein's World of Mathematics, Sierpiński Sieve Graph
MATHEMATICA
a[n_] := Module[{m}, If[n == 1, Return[2]]; m = 3^(n-2); 2^m*3^((m-1)/2)* (7*17/(2^4*3^3)*4^(n-1) + 2^2*13/3^3 - If[n == 2, 1/(2^2*3^2), 0])];
Array[a, 6] (* Jean-François Alcover, Dec 04 2018, from PARI *)
PROG
(PARI) A246958(n) = if(n==1, return(2)); my(m=3^(n-2)); 2^m * 3^((m-1)/2) * ( 7*17/(2^4*3^3)*4^(n-1) + 2^2*13/(3^3) - if(n==2, 1/(2^2*3^2) ) )
CROSSREFS
KEYWORD
nonn
AUTHOR
Max Alekseyev, Sep 08 2014
STATUS
approved