A222403 Triangle read by rows: left and right edges are A000217, interior entries are filled in using the Pascal triangle rule.

0, 1, 1, 3, 2, 3, 6, 5, 5, 6, 10, 11, 10, 11, 10, 15, 21, 21, 21, 21, 15, 21, 36, 42, 42, 42, 36, 21, 28, 57, 78, 84, 84, 78, 57, 28, 36, 85, 135, 162, 168, 162, 135, 85, 36, 45, 121, 220, 297, 330, 330, 297, 220, 121, 45, 55, 166, 341, 517, 627, 660, 627, 517, 341, 166, 55

Offset

0,4

Comments

In general, if the sequence defining the left and right edges is [a_0, a_1, ...], the row sums [s_0, s_1, ...] are given by s_0=a_0 and, for n>0,

s_n = 2a_n + Sum_{i=1..n-1} 2^(n-i) a_i.

Conversely, given the rows sums [s_0, s_1, ...], the edge sequence is [a_0, a_1, ...] where a_0=s_0 and, for n>0, a_n = (s_n - Sum_{i=1..n-1} s_i)/2.

Links

Robert Israel, Table of n, a(n) for n = 0..10010

Formula

G.f. as triangle: (1+x-4*x*y+x*y^2+x^2*y^2)*y/((1-y)^2*(-x*y+1)^2*(-x*y-y+1)). - Robert Israel, Apr 04 2018

Example

Triangle begins:
0
1, 1
3, 2, 3
6, 5, 5, 6
10, 11, 10, 11, 10
15, 21, 21, 21, 21, 15
21, 36, 42, 42, 42, 36, 21
28, 57, 78, 84, 84, 78, 57, 28
...

Maple

d:=[seq(n*(n+1)/2, n=0..14)];
f:=proc(d) local T, M, n, i;
M:=nops(d);
T:=Array(0..M-1, 0..M-1);
for n from 0 to M-1 do T[n, 0]:=d[n+1]; T[n, n]:=d[n+1]; od:
for n from 2 to M-1 do
for i from 1 to n-1 do T[n, i]:=T[n-1, i-1]+T[n-1, i]; od: od:
lprint("triangle:");
for n from 0 to M-1 do lprint(seq(T[n, i], i=0..n)); od:
lprint("row sums:");
lprint([seq( add(T[i, j], j=0..i), i=0..M-1)]);
end;
f(d);

Mathematica

t[n_, n_] := n*(n+1)/2; t[n_, 0] := n*(n+1)/2; t[n_, k_] := t[n, k] = t[n-1, k-1] + t[n-1, k]; Table[t[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 20 2014 *)

Crossrefs

Other triangles of this type: A007318, A051666, A134634, A222404, A222405.

Cf. A000217.

Row sums are A005803.

Sequence in context: A131990 A033771 A033795 * A033783 A033807 A371070

Adjacent sequences: A222400 A222401 A222402 * A222404 A222405 A222406

Keyword

nonn,tabl

Author

N. J. A. Sloane, Feb 18 2013

Status

approved