Euler's totient function applied to tribonacci numbers.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =12a(6) =8a(7) =20a(8) =54a(9) =148a(10) =136a(11) =144a(12) =612a(13) =1200a(14) =1344a(15) =2448a(16) =10506a(17) =16848a(18) =13824a(19) =22000a(20) =83232a(21) =148716a(22) =205368a(23) =377736a(24) =920160a(25) =1694088a(26) =1880304a(27) =3290112a(28) =14839968a(29) =22472640