Number of distinct quadratic residues mod 4^n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =44a(5) =172a(6) =684a(7) =2732a(8) =10924a(9) =43692a(10) =174764a(11) =699052a(12) =2796204a(13) =11184812a(14) =44739244a(15) =178956972a(16) =715827884a(17) =2863311532a(18) =11453246124a(19) =45812984492a(20) =183251937964a(21) =733007751852