Shifts 2 places left under binomial transform.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =9a(6) =23a(7) =65a(8) =199a(9) =654a(10) =2296a(11) =8569a(12) =33825a(13) =140581a(14) =612933a(15) =2795182a(16) =13298464a(17) =65852873a(18) =338694479a(19) =1805812309a(20) =9963840219a(21) =56807228074a(22) =334192384460