a(0)=1, a(1)=2 and, for n>1, a(n) = a(n-1) + 11*a(n-2).

Terms

a(0) =1a(1) =2a(2) =13a(3) =35a(4) =178a(5) =563a(6) =2521a(7) =8714a(8) =36445a(9) =132299a(10) =533194a(11) =1988483a(12) =7853617a(13) =29726930a(14) =116116717a(15) =443112947a(16) =1720396834a(17) =6594639251a(18) =25519004425a(19) =98060036186a(20) =378769084861