x <- 1:15

y1 <- c(16,27,45,74,122,201,331,546,900,1484,2447,4034,6651,10966,18080)

y2 <- c(6.77e+00, 9.16e-01, 1.24e-01, 1.68e-02, 2.27e-03, 3.07e-04,
        4.16e-05, 5.63e-06, 7.61e-07, 1.03e-07, 1.39e-08, 1.89e-09,
	2.55e-10, 3.46e-11, 4.68e-12)