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A212263 Main diagonal of symmetric array defined by the recurrence T(n,1)=1, T(1,k)=1, for n >= k: T(n,k) = Sum_{i=1..k-1} T(n-i,k), for n < k: T(n,k) = Sum_{i=1..n-1} T(k-i,n). 0
1, 1, 2, 5, 16, 58, 222, 869, 3438, 13672, 54518, 217706, 870036, 3478446, 13910128, 55632657, 222513784, 890019102, 3559999490, 14239834188, 56958988812, 227835217794, 911339311462, 3645353954182, 14581408883620 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) mod 2 = A023900(n) mod 2. The recurrence mentioned in the title is the same as the recurrence in array A191898 but without the minus signs.

LINKS

Table of n, a(n) for n=1..25.

FORMULA

Main diagonal of array defined by: T(n,1)=1, T(1,k)=1, n >= k: Sum_{i=1..k-1} T(n-i,k), n < k: Sum_{i=1..n-1} T(k-i,n).

MATHEMATICA

Clear[nn, t, n, k]; nn = 25; t[n_, 1] = 1; t[1, k_] = 1; t[n_, k_] := t[n, k] = If[n >= k, Sum[t[n - i, k], {i, 1, k - 1}], Sum[t[k - i, n], {i, 1, n - 1}]]; Table[t[n, n], {n, 1, nn}]

CROSSREFS

Cf. A023900, A191898.

Sequence in context: A286946 A184596 A149978 * A149979 A262441 A328296

Adjacent sequences:  A212260 A212261 A212262 * A212264 A212265 A212266

KEYWORD

nonn

AUTHOR

Mats Granvik, May 12 2012

STATUS

approved

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Last modified June 20 10:03 EDT 2021. Contains 345162 sequences. (Running on oeis4.)