It would not surprise me if gcc 4.8.x did not support index_sequence. And yes, it would be the libstdc++ that comes with the compiler, not the compiler itself.
FWIW, index_sequence *is* implemented in gcc 4.9.2, but it is only available post-c++11.
-- Marshall
Not sure if this is relevent, but I received the same error on VS2015 CTP 6. I changed the code to std::integer_sequence< std::size_t, I ... > to get around it. On a related note, on CTP6, Microsoft has changed the include paths for the CRT. For some reason some boost build generated files with names like 'b2_msvc_14.0_vcvarsall_amd64.cmd' were not regenerating after I upgraded to CTP6 which resulted in a stale INCLUDE environment variable an consequently, a failed build. Manually deleting the files corrected the problem. -- chris