数列{an}满足a1=1,nan+1=(n+1)an+n(n+1), n`in` N+
(1)证明:数列{`(a_(n))/(n)` }是等差数列;
(2)设bn=3n`*` `sqrt(a_(n))` ,求数列{`b_(n)` }的前n项和`S_(n)` .
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