%N a(n) = smallest k >= n such that k | (2^k + n).
%C Equally, a(n) = smallest k with 2^k mod k = k - n.
%F a(p-2) = p for p prime >= 5; a(2^k) = 2^k. - _David W. Wilson_
%Y Cf. A015910, A036236.
%A _Robert G. Wilson v_
%E Edited by _N. J. A. Sloane_, Jan 31 2009 at the suggestion of R. J. Mathar and T. D. Noe.
%E Restricted the range of k in the definition - _R. J. Mathar_, Mar 07 2010