

A117931


Inductive sumanddifference sequence.


2



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
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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(n1); for even n>=3, a(n)=least positive difference xy such that x,y are in F(n1) and xy is not in F(n1).


EXAMPLE

a(3)=3+4, a(4)=72, a(4)=3+6, a(5)=52, 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



