A213500 Rectangular array T(n,k): (row n) = b**c, where b(h) = h, c(h) = h + n - 1, n >= 1, h >= 1, and ** = convolution.
1, 4, 2, 10, 7, 3, 20, 16, 10, 4, 35, 30, 22, 13, 5, 56, 50, 40, 28, 16, 6, 84, 77, 65, 50, 34, 19, 7, 120, 112, 98, 80, 60, 40, 22, 8, 165, 156, 140, 119, 95, 70, 46, 25, 9, 220, 210, 192, 168, 140, 110, 80, 52, 28, 10, 286, 275, 255, 228, 196, 161, 125, 90
Offset: 1
Examples
Northwest corner (the array is read by southwest falling antidiagonals): 1, 4, 10, 20, 35, 56, 84, ... 2, 7, 16, 30, 50, 77, 112, ... 3, 10, 22, 40, 65, 98, 140, ... 4, 13, 28, 50, 80, 119, 168, ... 5, 16, 34, 60, 95, 140, 196, ... 6, 19, 40, 70, 110, 161, 224, ... T(6,1) = (1)**(6) = 6; T(6,2) = (1,2)**(6,7) = 1*7+2*6 = 19; T(6,3) = (1,2,3)**(6,7,8) = 1*8+2*7+3*6 = 40.
Links
- Clark Kimberling, Antidiagonals n = 1..60, flattened
Crossrefs
Cf. A000027.
Programs
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Mathematica
b[n_] := n; c[n_] := n t[n_, k_] := Sum[b[k - i] c[n + i], {i, 0, k - 1}] TableForm[Table[t[n, k], {n, 1, 10}, {k, 1, 10}]] Flatten[Table[t[n - k + 1, k], {n, 12}, {k, n, 1, -1}]] r[n_] := Table[t[n, k], {k, 1, 60}] (* A213500 *)
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PARI
t(n,k) = sum(i=0, k - 1, (k - i) * (n + i)); tabl(nn) = {for(n=1, nn, for(k=1, n, print1(t(k,n - k + 1),", ");); print(););}; tabl(12) \\ Indranil Ghosh, Mar 26 2017
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Python
def t(n, k): return sum((k - i) * (n + i) for i in range(k)) for n in range(1, 13): print([t(k, n - k + 1) for k in range(1, n + 1)]) # Indranil Ghosh, Mar 26 2017
Formula
T(n,k) = 4*T(n,k-1) - 6*T(n,k-2) + 4*T(n,k-3) - T(n,k-4).
T(n,k) = 2*T(n-1,k) - T(n-2,k).
G.f. for row n: x*(n - (n - 1)*x)/(1 - x)^4.
Comments