Positive integers k that divide 7^k + 3.

Terms

a(0) =1a(1) =2a(2) =4a(3) =5a(4) =26a(5) =205a(6) =2404a(7) =88171a(8) =1785134a(9) =2010899a(10) =58796834a(11) =639723359a(12) =657788549a(13) =2050134685a(14) =4809019972a(15) =6114530474a(16) =11931055777