A156031 Alternate A022941 and A143344.

1, 2, 3, 5, 4, 9, 6, 15, 7, 22, 8, 30, 10, 40, 11, 51, 12, 63, 13, 76, 14, 90, 16, 106, 17, 123, 18, 141, 19, 160, 20, 180, 21, 201, 23, 224, 24, 248, 25, 273, 26, 299, 27, 326, 28, 354, 29, 383, 31, 414, 32, 446, 33, 479, 34, 513, 35, 548, 36, 584, 37, 621, 38, 659, 39, 698

Offset

1,2

Comments

Eric Angelini's definition was: start with 1,2,3; then alternately adjoin either the sum of the last two terms or the smallest number not yet in the sequence.

Links

M. F. Hasler, Table of n, a(n) for n = 1..2001

Prog

(PARI) f="b156031.txt"; used=[]; write(f, c=1, " ", b=1); a=1; for(i=1, 1e3, used=setunion(used, Set(a+=b)); while(setsearch(used, b++), used=setminus(used, Set(b))); write(f, c++, " "a"\n", c++, " "b)) \\ M. F. Hasler, Nov 01 2009
(Haskell)
import Data.List (transpose)
a156031 n = a156031_list !! n
a156031_list = tail $ concat (transpose [a022941_list, a143344_list])
-- Reinhard Zumkeller, May 17 2013

Crossrefs

Cf. A022941, A143344, A167151, A005228, A030124.

Sequence in context: A269368 A075301 A352790 * A119475 A096116 A259431

Adjacent sequences: A156028 A156029 A156030 * A156032 A156033 A156034

Keyword

nonn

Author

N. J. A. Sloane, Nov 01 2009, based on a posting by Eric Angelini to the Sequence Fans Mailing List

Status

approved