a(n) = 2^n - 1 written backwards.

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =51a(5) =13a(6) =36a(7) =721a(8) =552a(9) =115a(10) =3201a(11) =7402a(12) =5904a(13) =1918a(14) =38361a(15) =76723a(16) =53556a(17) =170131a(18) =341262a(19) =782425a(20) =5758401a(21) =1517902a(22) =3034914a(23) =7068838a(24) =51277761a(25) =13445533a(26) =36880176a(27) =727712431a(28) =554534862a(29) =119078635