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%I #11 Feb 04 2018 03:20:10
%S 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,
%T 123,18,141,19,160,20,180,21,201,23,224,24,248,25,273,26,299,27,326,
%U 28,354,29,383,31,414,32,446,33,479,34,513,35,548,36,584,37,621,38,659,39,698
%N Alternate A022941 and A143344.
%C 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.
%H M. F. Hasler, <a href="/A156031/b156031.txt">Table of n, a(n) for n = 1..2001</a>
%o (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
%o (Haskell)
%o import Data.List (transpose)
%o a156031 n = a156031_list !! n
%o a156031_list = tail $ concat (transpose [a022941_list, a143344_list])
%o -- _Reinhard Zumkeller_, May 17 2013
%Y Cf. A022941, A143344, A167151, A005228, A030124.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Nov 01 2009, based on a posting by Eric Angelini to the Sequence Fans Mailing List
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