A138832 Concatenation of n-th Mersenne prime A000668(n) and n-th perfect number.
36, 728, 31496, 1278128, 819133550336, 1310718589869056, 524287137438691328, 21474836472305843008139952128, 23058430092136939512658455991569831744654692615953842176
Offset: 1
Examples
a(3)=31496 because A000668(3)=31 and A000396(3)=496.