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%I #2 Mar 30 2012 18:37:17
%S 1,12,66,255,903,2970,8571,23001,59763,145164,333693,751059,1623009,
%T 3363576,6872307,13677228,26351985,50309910,94392525,172538934,
%U 313558506,563064207,988996095,1730456433,3001805067,5106353439
%N A trisection of A161804: a(n) = A161804(3n) for n>=0.
%C G.f. of A161804 is exp( Sum_{n>=1} A002129(n) * 3*A038500(n) * q^n/n ),
%C where A002129 forms the l.g.f. of log[ Sum_{n>=0} x^(n(n+1)/2) ], and
%C A038500(n) is the highest power of 3 dividing n.
%e G.f.: T_0(q) = 1 + 12*q + 66*q^2 + 255*q^3 + 903*q^4 + 2970*q^5 +...
%o (PARI) {a(n)=local(L=sum(m=1, 3*n,3*3^valuation(m,3)*sumdiv(m, d, -(-1)^d*d)*x^m/m)+x*O(x^(3*n))); polcoeff(exp(L), 3*n)}
%Y Cf. A161804, other trisections: A161806 (T_1), A161807 (T_2).
%K nonn
%O 0,2
%A _Paul D. Hanna_, Jul 20 2009
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