A026052 (d(n)-r(n))/2, where d = A008778 and r is the periodic sequence with fundamental period (1,1,0,1).

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