Without any background S5, and S6.. could be anything. So tell us moreOriginally Posted by Decoder
about the origin of the problem.
Alternatively putting a Lagrangian Interpolating Polynomial (http://mathworld.wolfram.com/Lagrang...olynomial.html)
through the points gives S5=15641, and S6=28101.
The Online Encyclopedia of integer sequences knows nothing of this sequence.