The bottom entry in the forward difference table of the Euler totient function phi for 1..n.

Terms

a(0) =1a(1) =0a(2) =1a(3) =-2a(4) =5a(5) =-14a(6) =39a(7) =-102a(8) =247a(9) =-558a(10) =1197a(11) =-2494a(12) =5167a(13) =-10850a(14) =23311a(15) =-51132a(16) =113333a(17) =-250694a(18) =547871a(19) =-1175998a(20) =2475153a(21) =-5117486a(22) =10439895a(23) =-21142030a(24) =42777735a(25) =-86960284a(26) =178221401a(27) =-368541508a(28) =767762191a(29) =-1606535062