Number of free pure symmetric multifunctions in one symbol with n positions.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =5a(6) =12a(7) =25a(8) =57a(9) =128a(10) =296a(11) =688a(12) =1618a(13) =3839a(14) =9170a(15) =22065a(16) =53370a(17) =129807a(18) =317080a(19) =777887a(20) =1915247a(21) =4731932a(22) =11726476a(23) =29143123a(24) =72614115a(25) =181363151a(26) =453975928a(27) =1138697689a(28) =2861607677a(29) =7204169689