Binary XOR of 5^k as k varies from 0 to n.

Terms

a(0) =1a(1) =4a(2) =29a(3) =96a(4) =529a(5) =3620a(6) =13101a(7) =66048a(8) =325601a(9) =1653380a(10) =9189501a(11) =40187552a(12) =216562929a(13) =1143607140a(14) =5098589837a(15) =26660767488a(16) =161932208321a(17) =635945960964