a(n) = (48*n^4 + 32*n^6 + 36*n^8 + 32*n^12 + 19*n^16 + 24*n^18 + n^32) / 192.
a(n) = C(n,1) + 22409618*C(n,2) + 9651132365418*C(n,3) + 96038196404417832*C(n,4) + 120785673234798359850*C(n,5) + 40725205155234194765220*C(n,6) + 5464611173328028329053040*C(n,7) + 367782713912186945387883840*C(n,8) + 14373563321596798877701789800*C(n,9) + 359883141899402124632485810800*C(n,10) + 6184991837595074128351177096800*C(n,11) + 76711443861342809436413801659200*C(n,12) + 712777405284132776184971034460800*C(n,13) + 5104524541259652946568783959507200*C(n,14) + 28797485239301310151711610238720000*C(n,15) + 130163892496470993203014850790912000*C(n,16) + 477548461917280632356433595575936000*C(n,17) + 1436223810514558840121822575516416000*C(n,18) + 3566452148795758403208660387955200000*C(n,19) + 7348050481070906467554726390758400000*C(n,20) + 12594856495384277051085880584652800000*C(n,21) + 17969280084916069147800454551859200000*C(n,22) + 21302862405912312079825436975308800000*C(n,23) + 20896529603947922315711136828211200000*C(n,24) + 16837871283345549751877122560000000000*C(n,25) + 11021533432128296153318764634112000000*C(n,26) + 5764800913106992933428143603712000000*C(n,27) + 2351280741029830331492705206272000000*C(n,28) + 720354927933711780177833164800000000*C(n,29) + 155891316152123120086047129600000000*C(n,30) + 21242333189959633945791037440000000*C(n,31) + 1370473109029653802954260480000000*C(n,32), where the coefficient of C(n,k) is the number of colorings using exactly k colors.