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A056230
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Construct difference array so that (1) first row begins with 1, (2) every row is monotonic increasing, (3) no number appears more than once, (4) smallest number not yet used begins a new row. Sequence gives array read by antidiagonals.
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9
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1, 2, 3, 4, 6, 9, 7, 11, 17, 26, 12, 19, 30, 47, 73, 13, 25, 44, 74, 121, 194, 14, 27, 52, 96, 170, 291, 485, 15, 29, 56, 108, 204, 374, 665, 1150, 16, 31, 60, 116, 224, 428, 802, 1467, 2617, 18, 34, 65, 125, 241, 465, 893, 1695, 3162, 5779, 20, 38, 72, 137, 262
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Reinhard Zumkeller, Antidiagonals n=1..150 of array, flattened
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EXAMPLE
| Array begins
1 3 9 26 73 194 ...
.2 6 17 47 121 ...
. 4 11 30 74 ...
.. 7 19 44 ...
... 12 25 ...
.... 13 ...
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PROG
| (Haskell)
import Data.List (intersect, union, (\\))
a056230 n k = a056230_tabl !! (n-1) !! (k-1)
a056230_tabl = [1] : f [1] [2..] [1] where
f adiag (a:as) us | null (adiag' `intersect` us) =
adiag' : f adiag' (as \\ adiag') (us `union` adiag')
| otherwise = f adiag as us
where adiag' = scanl (+) a adiag
-- Reinhard Zumkeller, Nov 19 2011
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CROSSREFS
| Cf. A057153 (first row), A200379 (second row), A052474 (main diagonal), A057154 (numbers not used), A056231, A056232, A056233, A056234.
Sequence in context: A159849 A098168 A035312 * A119919 A036561 A082976
Adjacent sequences: A056227 A056228 A056229 * A056231 A056232 A056233
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KEYWORD
| nice,nonn,easy,tabl
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AUTHOR
| Jonas Wallgren (jonwa(AT)ida.liu.se), Jul 30, 2000.
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