A250090 a(0)=1; for n>0, a(n) is the number not yet used which yields the smallest possible positive sum_{k=0..n} (-1)^(a(k)+1)*a(k).

1, 0, 3, 2, 5, 6, 7, 4, 9, 12, 11, 10, 13, 14, 15, 8, 17, 24, 19, 18, 21, 22, 23, 20, 25, 28, 27, 26, 29, 30, 31, 16, 33, 48, 35, 34, 37, 38, 39, 36, 41, 44, 43, 42, 45, 46, 47, 40, 49, 56, 51, 50, 53, 54, 55, 52, 57, 60, 59, 58, 61, 62, 63, 32, 65, 96, 67, 66, 69, 70, 71, 68, 73, 76, 75, 74, 77, 78, 79, 72, 81, 88, 83, 82, 85, 86, 87, 84, 89, 92, 91

Offset

0,3

Comments

Odd terms are added, even terms are subtracted. At each step, the next term is chosen among numbers which did not yet occur, as to minimize this sum.

Links

Table of n, a(n) for n=0..90.

E. Angelini, Minimizing Q, SeqFan list, Nov 11 2014.

Prog

(PARI) A250090(n=100, a=1, Q=0, u=[])={for(n=1, n, print1(a", "); u=setunion(u, Set(a)); Q-=(-1)^a*a; forstep(k=2-Q%2, Q, 2, setsearch(u, Q-k)&&next; a=Q-k; next(2)); forstep(k=1, 9e9, 2, setsearch(u, k)&&next; a=k; next(2))); a} \\ returns a(n) and prints out a(k) for 0<=k<n.

Crossrefs

Cf. A250072.

Sequence in context: A153152 A153153 A175058 * A334999 A154437 A305428

Adjacent sequences: A250087 A250088 A250089 * A250091 A250092 A250093

Keyword

nonn

Author

Eric Angelini and M. F. Hasler, Nov 11 2014

Status

approved