31675383749domain: NAppears in sequencesLet p be the n-th prime and let g be the order of 2 mod p (see A014664). Then if g is even, a(n) = p*(2^(g/2) - 1), otherwise a(n) = 2^g - 1.at n=15A135546Length of all the nontrivial cycles of the Ducci map modulo 2 for the dimensions in A138004.at n=13A138006