Number of irredundant sets in the n-helm graph.

Terms

a(0) =5a(1) =13a(2) =35a(3) =113a(4) =355a(5) =1105a(6) =3435a(7) =10625a(8) =32723a(9) =100433a(10) =307323a(11) =937985a(12) =2856547a(13) =8682897a(14) =26349835a(15) =79850241a(16) =241679859a(17) =730700881a(18) =2207155867a(19) =6661493633a(20) =20090908803a(21) =60555714705a(22) =182419600683a(23) =549259559297