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A216957 as a simple table

na(n)
12
22
34
46
512
620
740
874
9148
10286
11568
121118
132228
144412
158788
1617480
1734836
1869392
19138388
20275942
21550560
221098516
232192572
244376666
258738324
2617448308
2734845304
2869594398
29139011816
30277691852
31554767744
321108378658
332214594580
344425117884
358842583584
3617670722600
3735314182976
3870576759892
39141055781836

[2,2,4,6,12,20,40,74,148,286,568,1118,2228,4412,
 8788,17480,34836,69392,138388,275942,550560,
 1098516,2192572,4376666,8738324,17448308,34845304,
 69594398,139011816,277691852,554767744,1108378658,
 2214594580,4425117884,8842583584,17670722600,
 35314182976,70576759892,141055781836]