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 A026052 (d(n)-r(n))/2, where d = A008778 and r is the periodic sequence with fundamental period (1,1,0,1). 1
 2, 6, 13, 22, 35, 52, 74, 100, 132, 170, 215, 266, 325, 392, 468, 552, 646, 750, 865, 990, 1127, 1276, 1438, 1612, 1800, 2002, 2219, 2450, 2697, 2960, 3240, 3536, 3850, 4182, 4533, 4902, 5291, 5700, 6130, 6580, 7052, 7546, 8063, 8602, 9165, 9752, 10364, 11000, 11662, 12350, 13065, 13806, 14575 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS FORMULA a(n)=(n + 2)*(n^2 + 10*n + 15)/12 - 0.375 + 0.125*( - 1)^n - 0.25*cos(n*Pi/2) [From Richard Choulet, Dec 13 2008] CROSSREFS Sequence in context: A194138 A194137 A226292 * A049616 A258603 A064960 Adjacent sequences:  A026049 A026050 A026051 * A026053 A026054 A026055 KEYWORD nonn AUTHOR STATUS approved

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Last modified April 9 10:52 EDT 2020. Contains 333348 sequences. (Running on oeis4.)