A117263 - OEIS

%I #6 Jun 06 2020 21:31:03

%S 1,2,7,64,1729,140050,34032151,24809438080,54258241080961,

%T 355988319732185122,7006918097288599756327,

%U 413751506726794527011353024,73294838162131470076480154142529

%N Row sums of triangle A117262; also, self-convolution of A117264.

%F a(n) = Sum_{k=0..n} 3^( n*(n-1)/2 - k*(k-1)/2 ).

%F G.f. A(x) satisfies: A(x) = 1/(1 - x) + x * A(3*x). - _Ilya Gutkovskiy_, Jun 06 2020

%o (PARI) a(n)=sum(k=0,n,3^((n-k)*(n+k-1)/2))

%Y Cf. A117261, A117262, A117264.

%K nonn

%O 0,2

%A _Paul D. Hanna_, Mar 14 2006