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

Author

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

Keywords

• nonn
• nice
• easy

Examples

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

Links

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

Crossrefs

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

Programs

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