a(1)=a(2)=1, a(n) = ceiling(Pi*a(n-1) - a(n-2)), n>2.

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =26a(5) =73a(6) =204a(7) =568a(8) =1581a(9) =4399a(10) =12239a(11) =34051a(12) =94736a(13) =263571a(14) =733297a(15) =2040150a(16) =5676024a(17) =15791606a(18) =43934770a(19) =122233545a(20) =340073237a(21) =946138039a(22) =2632307076a(23) =7323498533a(24) =20375142114a(25) =56686898249a(26) =157712000980