Sum of two consecutive squares of Lucas 3-step numbers (A001644).

Terms

a(0) =10a(1) =10a(2) =58a(3) =170a(4) =562a(5) =1962a(6) =6562a(7) =22202a(8) =75242a(9) =254330a(10) =860474a(11) =2911226a(12) =9848050a(13) =33316090a(14) =112707970a(15) =381286954a(16) =1289885834a(17) =4363653034a(18) =14762129274a(19) =49939929610a(20) =168945571442a(21) =571538767370