A117931 Inductive sum-and-difference sequence.

1, 2, 7, 5, 9, 3, 10, 4, 14, 6, 19, 8, 23, 11, 25, 12, 28, 13, 31, 15, 33, 16, 35, 17, 38, 18, 41, 20, 43, 21, 46, 22, 50, 24, 53, 26, 56, 27, 59, 29, 62, 30, 66, 32, 70, 34, 73, 36, 76, 37, 79, 39, 82, 40, 86, 42, 89, 44, 92, 45, 95, 47, 97, 48, 100, 49, 103, 51, 106, 52, 109

Offset

1,2

Comments

A permutation of the natural numbers.

Links

Table of n, a(n) for n=1..71.

Formula

a(1)=1, a(2)=2 and for n>=3 let F(n)={a(1),a(2),...,a(n)}. For odd n>=3, a(n)=x+y where x,y are the least positive integers not in F(n-1); for even n>=3, a(n)=least positive difference x-y such that x,y are in F(n-1) and x-y is not in F(n-1).

Example

a(3)=3+4, a(4)=7-2, a(4)=3+6, a(5)=5-2, a(6)=4+6.

Crossrefs

Cf. A117932, A117933.

Sequence in context: A198737 A010593 A332322 * A011051 A024691 A220606

Adjacent sequences: A117928 A117929 A117930 * A117932 A117933 A117934

Keyword

nonn

Author

Clark Kimberling, Apr 03 2006

Status

approved