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 A027044 a(n) = Sum_{k=0..2n} (k+1) * A027023(n,2n-k). 2
 1, 6, 19, 56, 165, 486, 1435, 4248, 12601, 37438, 111367, 331608, 988181, 2946662, 8791447, 26241632, 78359825, 234069830, 699404127, 2090385216, 6249236653, 18686125070, 55884824535, 167164064984, 500102988889 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 MAPLE T:= proc(n, k) option remember;       if k<3 or k=2*n then 1     else add(T(n-1, k-j), j=1..3)       fi     end: seq(add((k+1)*T(n, 2*n-k), k=0..2*n), n=0..30); # G. C. Greubel, Nov 04 2019 MATHEMATICA T[n_, k_]:= T[n, k]= If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]; Table[Sum[(k+1)*T[n, 2*n-k], {k, 0, 2*n}], {n, 0, 30}] (* G. C. Greubel, Nov 04 2019 *) PROG (Sage) @CachedFunction def T(n, k):     if (k<3 or k==2*n): return 1     else: return sum(T(n-1, k-j) for j in (1..3)) [sum((k+1)*T(n, 2*n-k) for k in (0..2*n)) for n in (0..30)] # G. C. Greubel, Nov 04 2019 CROSSREFS Sequence in context: A176883 A274599 A286184 * A057571 A238055 A272227 Adjacent sequences:  A027041 A027042 A027043 * A027045 A027046 A027047 KEYWORD nonn AUTHOR STATUS approved

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Last modified July 28 03:49 EDT 2021. Contains 346316 sequences. (Running on oeis4.)