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%I #21 Jul 01 2022 10:21:58
%S 6,8,10,15,21,28,36,45,55,66,78,91,105,120,136,153,171,190,210,231,
%T 253,276,300,325,351,378,406,435,465,496,528,561,595,630,666,703,741,
%U 780,820,861,903,946,990,1035,1081,1128,1176,1225,1275,1326,1378,1431,1485,1540
%N 2nd subdiagonal of the triangle A350292.
%H Harvey P. Dale, <a href="/A350295/b350295.txt">Table of n, a(n) for n = 3..1000</a>
%H Heiko Harborth and Hauke Nienborg, <a href="https://www.researchgate.net/publication/266861957_Saturated_vertex_Turan_numbers_for_cube_graphs">Saturated vertex Turán numbers for cube graphs</a>, Congr. Num. 208 (2011), 183-188.
%H Mathonline, <a href="http://mathonline.wikidot.com/cube-graphs">Cube Graphs</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F a(n) = binomial(n, 2) = A000217(n-1) for n > 4 with a(3) = 6 and a(4) = 8 (see Theorem 3 in Harborth and Nienborg).
%F O.g.f.: x^3*(2*x^4 - 3*x^3 - 4*x^2 + 10*x - 6)/(x - 1)^3.
%F E.g.f.: x^2*(x^2 + 6*x + 6*exp(x) - 6)/12.
%F a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 7.
%t Join[{6,8},Table[Binomial[n,2],{n,5,56}]]
%t LinearRecurrence[{3,-3,1},{6,8,10,15,21},60] (* _Harvey P. Dale_, Jul 01 2022 *)
%Y Cf. A000217, A112355, A161680, A350292.
%K nonn,easy
%O 3,1
%A _Stefano Spezia_, Dec 23 2021
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