A339573 - OEIS

A339573

a(n) = floor(n*(n+1)/6) - 1.

0, 1, 2, 4, 6, 8, 11, 14, 17, 21, 25, 29, 34, 39, 44, 50, 56, 62, 69, 76, 83, 91, 99, 107, 116, 125, 134, 144, 154, 164, 175, 186, 197, 209, 221, 233, 246, 259, 272, 286, 300, 314, 329, 344, 359, 375, 391, 407, 424, 441, 458, 476, 494, 512, 531, 550, 569, 589, 609, 629, 650, 671, 692

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OFFSET

2,3

COMMENTS

a(n) = A001840(n-1)-1.

LINKS

Table of n, a(n) for n=2..64.

Bernhard Ganter, Notes on Integer Partitions, Technische Universität Dresden (2020); See Prop. 3.

Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).

FORMULA

G.f.: x^3*(-1-x^2+x^3) / ( (1+x+x^2)*(x-1)^3 ). - R. J. Mathar, Jan 14 2021

MATHEMATICA