A056234 Form an array with 3 rows: row 1 begins with 1; all rows are increasing; each entry is sum of 2 entries above it; each number appears at most once; smallest unused number is appended to first row if possible. Sequence gives numbers not used.

5, 24, 29, 42, 72, 90, 93, 112, 120, 125, 138, 158, 172, 175, 192, 197, 200, 205, 208, 213, 218, 230, 235, 264, 282, 285, 302, 305, 310, 321, 324, 329, 333, 364, 372, 375, 378, 386, 416, 430, 439, 452, 455, 477, 496, 504, 509, 522, 542, 556

Offset

1,1

Links

Zak Seidov and Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Example

Array begins
1 2 4 7 8 10 12 ...
.3 6 11 15 18 ...
. 9 17 26 33 ...

Prog

(Haskell)
a056234 n = a056234_list !! (n-1)
a056234_list = notUsed 1 a056231_list a056232_list a056233_list where
   notUsed x us'@(u:us) vs'@(v:vs) ws'@(w:ws)
    | x == u = notUsed (x + 1) us vs' ws'
    | x == v = notUsed (x + 1) us' vs ws'
    | x == w = notUsed (x + 1) us' vs' ws
    | otherwise = x : notUsed (x + 1) us' vs' ws'
-- Reinhard Zumkeller, Nov 07 2011

Crossrefs

Cf. A056231, A056232, A056233. See also A057153, A052474, A057154, A056230.

Sequence in context: A333633 A222355 A335352 * A030766 A063143 A006145

Adjacent sequences: A056231 A056232 A056233 * A056235 A056236 A056237

Keyword

nonn,nice,easy

Author

N. J. A. Sloane, E. M. Rains, Aug 22 2000

Status

approved