Number of 4-partitions of the fan graph F_{1,n} where every triangle uses exactly 2 parts.

Terms

a(0) =1a(1) =5a(2) =19a(3) =61a(4) =180a(5) =500a(6) =1335a(7) =3459a(8) =8767a(9) =21839a(10) =53674a(11) =130492a(12) =314493a(13) =752537a(14) =1790139a(15) =4237593a(16) =9990280a(17) =23471780a(18) =54986827a(19) =128501527a(20) =299678439a(21) =697644539a(22) =1621649262a(23) =3764596716a(24) =8729693569a(25) =20223978269a(26) =46814365891a(27) =108289428757a(28) =250339614588a(29) =578423423444