Truncated triangular numbers: a(n)=n*(n+1)/2-3*t*(t+1)/2, t=5.
0, 10, 21, 33, 46, 60, 75, 91, 108, 126, 145, 165, 186, 208, 231, 255, 280, 306, 333
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Fri Mar 12 10:09:44 CET 2010 [seqfan] editing A000217 Triangular numbers (long message)