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%I #8 May 22 2015 10:38:08
%S 1,2,6,7,11,20,21,25,34,50,51,55,64,80,105,106,110,119,135,160,196,
%T 197,201,210,226,251,287,336,337,341,350,366,391,427,476,540,541,545,
%U 554,570,595,631,680,744,825,826,830,839,855,880,916,965,1029,1110,1210
%N Square-pyramid-tree numbers: a(n) = sum(b(m),m=1..n), b(m) = 1^2, 1^2,2^2, 1^2,2^2,3^2,.. = (A002260)^2.
%H Ivan Neretin, <a href="/A051678/b051678.txt">Table of n, a(n) for n = 1..5050</a>
%F a(n * (n + 1)/2 + m) = 1/12 * n * (n + 2) * (n + 1)^2 + 1/6 * m * (m + 1) * (2 * m + 1) = A002415(n) + A000330(m), m = 0...n + 1, n = 1, 2, 3..
%t Table[n^2 (n^2 - 1)/12 + m (m + 1) (2 m + 1)/6, {n, 10}, {m, n}] // Flatten (* _Ivan Neretin_, May 22 2015 *)
%Y Cf. A002260, A000330, A002415.
%K easy,nice,nonn
%O 1,2
%A Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de)
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