[1] area formula = number of cells for 477 admissible pairs a,b<=30
[2] (n,2n) = (n,2n-1) = (n,2n-2) as cell sets, same invariant, n<=30
[3] mirror (i,j,k)->(i,k,j): B(a,b) -> B(b,a); rotation (k,i,j) preserves B(a,b); a,b<=24
[4] classification of admissible a<=b<=120: {'res1': 1220, 'res2': 1239, 'b=2a': 59, 'I=0': 7, 'I<0': 249, 'R7': 944}
    slice sizes d=0..9: [0, 0, 0, 2, 5, 9, 14, 20, 27, 35]  formula (d-2)(d+1)/2 for d=3..9: [2, 5, 9, 14, 20, 27, 35]
    |R7, b<=45| = 107  |R7, b<=60| = 206
    R7 with b=61: [32, 35, 38, 41, 44, 47, 50, 53]
    R7 in window max<=14: [(6, 9), (7, 11), (9, 12), (8, 13), (10, 14)]
    row J=1 inside b<=60: 26 benzels (n,2n-3) with n from 6
[5] T103: 18 table entries reproduced, 0 mismatches
[5] T013: 18 table entries reproduced, 0 mismatches
[6] Propp's T103 table (41 entries, a,b<=10): entry > 0 exactly when I(a,b) >= 0
FAILURES: 0  (0.4s)
