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A117263
Row sums of triangle A117262; also, self-convolution of A117264.
3
1, 2, 7, 64, 1729, 140050, 34032151, 24809438080, 54258241080961, 355988319732185122, 7006918097288599756327, 413751506726794527011353024, 73294838162131470076480154142529
OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} 3^( n*(n-1)/2 - k*(k-1)/2 ).
G.f. A(x) satisfies: A(x) = 1/(1 - x) + x * A(3*x). - Ilya Gutkovskiy, Jun 06 2020
PROG
(PARI) a(n)=sum(k=0, n, 3^((n-k)*(n+k-1)/2))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 14 2006
STATUS
approved