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A081197
Diagonal sums of A081130.
2
0, 0, 0, 1, 4, 13, 44, 162, 643, 2724, 12259, 58423, 293902, 1555743, 8640526, 50222288, 304792741, 1927313470, 12673784445, 86517541197, 612134881624, 4482215342305, 33919417267456, 264951302794510, 2133720505175351
OFFSET
0,5
LINKS
FORMULA
a(n) = Sum_{k=1..n-2} k^(n-k-2)*binomial(n-k, 2).
a(n) = Sum_{k=0..n-1} (n-k)^(k-2)*binomial(k, 2). - G. C. Greubel, May 15 2021
MAPLE
A081197 := proc(n)
add(k^(n-k-2)*binomial(n-k, 2), k=1..n-2) ;
end proc: # R. J. Mathar, Feb 13 2015
MATHEMATICA
Table[Sum[k^(n-k-2)*Binomial[n-k, 2], {k, n-2}], {n, 0, 30}] (* G. C. Greubel, May 15 2021 *)
PROG
(Magma) [n lt 3 select 0 else (&+[j^(n-j-2)*Binomial(n-j, 2): j in [1..n-2]]): n in [0..30]]; // G. C. Greubel, May 15 2021
(Sage) [sum( (n-k)^(k-2)*binomial(k, 2) for k in (0..n-1) ) for n in (0..30)] # G. C. Greubel, May 15 2021
CROSSREFS
Cf. A081130.
Sequence in context: A045652 A149430 A124463 * A005490 A174299 A351028
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Mar 11 2003
EXTENSIONS
Terms corrected by G. C. Greubel, May 15 2021
STATUS
approved