# A193129 Number of spanning trees of the n-barbell graph. # M. F. Hasler, Table of n, a(n) for n = 0..32</a> # (corrected by Georg Fischer, 20 Jan 2019: prefix a(0..2)) 0 1 1 1 2 1 3 9 4 256 5 15625 6 1679616 7 282475249 8 68719476736 9 22876792454961 10 10000000000000000 11 5559917313492231481 12 3833759992447475122176 13 3211838877954855105157369 14 3214199700417740936751087616 15 3787675244106352329254150390625 16 5192296858534827628530496329220096 17 8193465725814765556554001028792218849 18 14747559712960682275277163588165279154176 19 30034640110980377619945846078500632729311721 20 68719476736000000000000000000000000000000000000 21 175522663228862486625127968549968702993144556569961 22 497630777616951325132715326372819220817654565543346176 23 1558005952997140033806173725098810522409738596181909282129 24 5361602775518515172309436468072356318555971195252167489355776 25 20194839173657902218540251271239327479634084738790988922119140625 26 82931725705091616965254232438514566604250680379656647571775292440576 27 369988485035126972924700782451696644186473100389722973815184405301748249 28 1787383027988360473982812052191328276130059755787807872687032756955267465216 29 9321630555798640999650267840597716238267698470229978898792541514288701586888281 30 52334763302736053721351152100000000000000000000000000000000000000000000000000000000 31 315484656553506999764735341936345403185656243600798222000056699762298322786077554101441 32 2037035976334486086268445688409378161051468393665936250636140449354381299763336706183397376