Secant numbers: 1, 1, 5, 61, 1385, 50521, 2702765
Quartic reciprocal: 1, 1, 69, 33661, 60376809
Signed Euler difference coordinates: 1, -2, 8, -80, 1664
Spacing-two lane: 1, 5, 1385; differences: 1, 4, 1376
Refinement: 2*4 + 1376 = 1384
Prime residual: 2*(-2) + 8 = 4
Newton residual orders: 2, 4, 8, 16, at least 32
PASS: Euler packets, polynomials and residuals
