A Pellian-related recursive sequence.

Terms

a(0) =1a(1) =7a(2) =36a(3) =175a(4) =841a(5) =4032a(6) =19321a(7) =92575a(8) =443556a(9) =2125207a(10) =10182481a(11) =48787200a(12) =233753521a(13) =1119980407a(14) =5366148516a(15) =25710762175a(16) =123187662361a(17) =590227549632