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A156580 Triangle read by rows: t(n,k)=If[2*(k - 1/2) == n, 2*(n + k - 4) + (-1)^ n, If[Floor[n/2] > (k - 1), 2*(n + k - 4), 2*(2*n - k - 3)]]. 0
1, 1, 1, 1, 2, 1, 1, 4, 4, 1, 1, 6, 7, 6, 1, 1, 8, 10, 10, 8, 1, 1, 10, 12, 13, 12, 10, 1, 1, 12, 14, 16, 16, 14, 12, 1, 1, 14, 16, 18, 19, 18, 16, 14, 1, 1, 16, 18, 20, 22, 22, 20, 18, 16, 1, 1, 18, 20, 22, 24, 25, 24, 22, 20, 18, 1, 1, 20, 22, 24, 26, 28, 28, 26, 24, 22, 20, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Row sums are:

{1, 2, 4, 10, 21, 38, 59, 86, 117, 154, 195, 242,...}.

Sequence is designed to be increasing to the symmetrical center

with only odd being first and last and odd n middle,

LINKS

Table of n, a(n) for n=1..78.

FORMULA

t(n,k)=If[2*(k - 1/2) == n, 2*(n + k - 4) + (-1)^ n, If[Floor[n/2] > (k - 1), 2*(n + k - 4), 2*(2*n - k - 3)]].

EXAMPLE

{1},

{1, 1},

{1, 2, 1},

{1, 4, 4, 1},

{1, 6, 7, 6, 1},

{1, 8, 10, 10, 8, 1},

{1, 10, 12, 13, 12, 10, 1},

{1, 12, 14, 16, 16, 14, 12, 1},

{1, 14, 16, 18, 19, 18, 16, 14, 1},

{1, 16, 18, 20, 22, 22, 20, 18, 16, 1},

{1, 18, 20, 22, 24, 25, 24, 22, 20, 18, 1},

{1, 20, 22, 24, 26, 28, 28, 26, 24, 22, 20, 1}

MATHEMATICA

Clear[A, n, k, m, e];

A[n_, 1] := 1; A[n_, n_] := 1; A[3, 2] := 2;

A[n_, k_] := If[2*(k - 1/2) == n, 2*(n + k - 4) + (-1)^n, If[Floor[n/2] > ( k - 1), 2*(n + k - 4), 2*(2*n - k - 3)]];

Table[Table[A[n, k], {k, 1, n}], {n, 12}];

Flatten[%]

CROSSREFS

Sequence in context: A026386 A147532 A283796 * A157528 A132731 A128966

Adjacent sequences:  A156577 A156578 A156579 * A156581 A156582 A156583

KEYWORD

nonn,tabl,uned

AUTHOR

Roger L. Bagula, Feb 10 2009

STATUS

approved

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Last modified October 14 05:08 EDT 2019. Contains 327995 sequences. (Running on oeis4.)