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A051677 Tetrahedron-tree numbers: a(n)=sum(b(m),m=1..n), b(m)=1, 1,3, 1,3,6, 1,3,6,10,..., 1,2,...,i*(i+1)2. 1
1, 2, 5, 6, 9, 15, 16, 19, 25, 35, 36, 39, 45, 55, 70, 71, 74, 80, 90, 105, 126, 127, 130, 136, 146, 161, 182, 210, 211, 214, 220, 230, 245, 266, 294, 330, 331, 334, 340, 350, 365, 386, 414, 450, 495, 496, 499, 505, 515, 530, 551, 579, 615, 660, 715, 716, 719 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n*(n+1)/2+m) = n*(n+1)*(n+2)*(n+3)/24 + m*(m+1)*(m+2)/6 = A000332(n)+A000292(m), m=0...n+1, n=1, 2, 3, ..
MATHEMATICA
With[{nn=20}, Accumulate[Flatten[Table[Take[Accumulate[Range[nn]], n], {n, nn}]]]] (* Harvey P. Dale, Jan 29 2012 *)
CROSSREFS
Sequence in context: A169779 A326118 A301791 * A122965 A350988 A226810
KEYWORD
easy,nice,nonn
AUTHOR
Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de)
STATUS
approved

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Last modified May 29 08:50 EDT 2024. Contains 372926 sequences. (Running on oeis4.)