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A114751 The following triangle contains n consecutive numbers beginning from n in ascending order if n is odd else in descending order. Sequence contains the triangle by rows. 2
1, 3, 2, 3, 4, 5, 7, 6, 5, 4, 5, 6, 7, 8, 9, 11, 10, 9, 8, 7, 6, 7, 8, 9, 10, 11, 12, 13, 15, 14, 13, 12, 11, 10, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

a(n) = (3*t+2-t*(-1)^(t-1))/2-(1+(-1)^t)*(j-1)/2+(1-(-1)^t)*(j-1)/2, where j = (t*t+3*t+4)/2-n, t=floor((-1+sqrt(8*n-7))/2). - Boris Putievskiy, Jan 30 2013

EXAMPLE

1

3 2

3 4 5

7 6 5 4

5 6 7 8 9

11 10 9 8 7 6

...

MAPLE

for n from 1 to 14 do if n mod 2 = 1 then print(seq(k, k=n..2*n-1)) else print(seq(2*n-k, k=1..n)) fi od; # yields sequence in triangular form (Deutsch)

CROSSREFS

Cf. A114752, A114753, A210530.

Sequence in context: A091563 A161985 A035366 * A211947 A220071 A132408

Adjacent sequences:  A114748 A114749 A114750 * A114752 A114753 A114754

KEYWORD

easy,nonn,tabl

AUTHOR

Amarnath Murthy, Nov 15 2005

EXTENSIONS

More terms from Emeric Deutsch, Jan 26 2006

STATUS

approved

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Last modified December 22 04:20 EST 2014. Contains 252328 sequences.