First differences of A261234.

Terms

a(0) =1a(1) =3a(2) =7a(3) =17a(4) =45a(5) =122a(6) =334a(7) =915a(8) =2511a(9) =6906a(10) =19039a(11) =52691a(12) =146641a(13) =410734a(14) =1157321a(15) =3276419a(16) =9307640a(17) =26509145a(18) =75669108a(19) =216483760a(20) =620847130a(21) =1784898316a(22) =5143127022a(23) =14847548759a(24) =42923323624a(25) =124213679008a(26) =359730306331