Number of mutual-visibility sets in the n-helm graph.

Terms

a(0) =57a(1) =159a(2) =380a(3) =836a(4) =2293a(5) =6682a(6) =19819a(7) =59200a(8) =177313a(9) =531622a(10) =1594519a(11) =4783180a(12) =14349133a(13) =43046962a(14) =129140419a(15) =387420760a(16) =1162261753a(17) =3486784702a(18) =10460353519a(19) =31381059940a(20) =94143179173a(21) =282429536842a(22) =847288609819