A278133 - OEIS

A278133

The sum of the heights of all bargraphs of semiperimeter n (n>=2).

1, 3, 10, 32, 101, 318, 1003, 3173, 10071, 32071, 102453, 328260, 1054620, 3396757, 10965653, 35475159, 114989969, 373400210, 1214529314, 3956450250, 12906762704, 42159475998, 137877383739, 451403471067, 1479329370617, 4852295325254, 15928202158814, 52321416289743, 171966242037941, 565480887258368, 1860228812665716, 6121446895971437

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OFFSET

2,2

LINKS

Table of n, a(n) for n=2..33.

A. Blecher, C. Brennan, A. Knopfmacher and H. Prodinger, The height and width of bargraphs, Discrete Applied Math. 180, (2015), 36-44 (see pp. 41-42).

FORMULA

a(n) = Sum_{k>=0} k*A278132(n,k).

EXAMPLE

a(4)=10; indeed, the bargraphs of semiperimeter 4 correspond to the compositions [3],[1,2],[2,2],[2,1],[1,1,1] and the sum of their heights is 3+2+2+2+1=10.

MAPLE

x := z: y := z: eq := G(h) = x*(y+G(h))+y*G(h-1)+x*(y+G(h))*G(h-1): ic := G(1) = x*y/(1-x): sol := simplify(rsolve({eq, ic}, G(h))): for j to 17 do g[j] := factor(simplify(rationalize(simplify(subs(h = j, sol))))) end do: H[1] := x*y/(1-x): for j from 2 to 50 do H[j] := factor(g[j]-g[j-1]) end do: for j to 17 do Hser[j] := series(H[j], z = 0, 50) end do: T := proc (n, k) coeff(Hser[k], z, n) end proc: seq(add(k*T(n, k), k = 1 .. n-1), n = 2 .. 45);

MATHEMATICA

x = y = z;

eq = G[h] == x*(y + G[h]) + y*G[h - 1] + x*(y + G[h])*G[h - 1];

ic = G[1] == x*y/(1 - x);

sol = RSolve[{eq , ic}, G[h], h];

For[j = 1, j <= 17, j++, g[j] = G[h] /. sol /. h -> j];

H[1] = x*y/(1 - x);

For[j = 2, j <= 50, j++, H[j] = g[j] - g[j - 1]];

For[j = 1, j <= 17, j++, Hser[j] = Series[H[j][[1]], {z, 0, 50}]];

T[n_, k_] := Coefficient[Hser[k], z, n];

a[n_] := Sum[k*T[n, k], {k, 1, n - 1}];

Table[a[n], {n, 2, 45}] (* Jean-François Alcover, Sep 14 2024, after Maple program *)