OFFSET

1,2

COMMENTS

If the restriction "increasing" is removed sequence A094870 is obtained.

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..5000

EXAMPLE

3 is out because of 1,2,3. 7 is out because of 1,4,7.

8 is allowed even though 2,5,8 appears in the sequence, because 2, 5, and 8 are not spaced equidistant within the sequence.

MAPLE

lim:=61: a[1]:=1:a[2]:=2: for n from 3 to lim do na := {}: for j from 1 to floor((n-1)/2) do na := na union {2*a[n-j]-a[n-2*j]}: od: for j from a[n-1]+1 do if(not member(j, na))then a[n]:=j:break: fi: od:od: seq(a[n], n=1..lim); # Nathaniel Johnston, Jun 16 2011

CROSSREFS

KEYWORD

nonn,easy

AUTHOR

Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 20 2004

STATUS

approved