If m is even and 2^m-m-1 is prime then 2^(m-1)*(2^m-m-1) is a term in A135470. 88, 518656, 134094848 and 2146926592 are the only terms of this form <= 10^12. Listed below are 10 terms of this form > 10^12. Donovan Johnson, Nov 15 2013 2^(26-1)*(2^26-26-1) = 2251798907715584 (16 digits) 2^(50-1)*(2^50-50-1) = 633825300114085990300727115776 (30 digits) 2^(56-1)*(2^56-56-1) = 2596148429267411760623818083663872 (34 digits) 2^(70-1)*(2^70-70-1) = 696898287454081973131080193484793195790336 (42 digits) 2^(116-1)*(2^116-116-1) = 345087...889792 (70 digits) 2^(2072-1)*(2^2072-2072-1) = 146984...034304 (1248 digits) 2^(6250-1)*(2^6250-6250-1) = 374900...909376 (3763 digits) 2^(13670-1)*(2^13670-13670-1) = 722855...851136 (8230 digits) 2^(14216-1)*(2^14216-14216-1) = 383536...100992 (8559 digits) 2^(14626-1)*(2^14626-14626-1) = 268165...120384 (8806 digits)