a(n) = |{m : multiplicative order of 7 mod m=n}|.

Terms

a(0) =4a(1) =6a(2) =8a(3) =26a(4) =4a(5) =42a(6) =12a(7) =48a(8) =52a(9) =66a(10) =12a(11) =778a(12) =4a(13) =138a(14) =80a(15) =300a(16) =12a(17) =528a(18) =12a(19) =1430a(20) =72a(21) =138a(22) =28a(23) =15216a(24) =24a(25) =66a(26) =1216a(27) =966a(28) =28a(29) =3630