OFFSET
1,3
COMMENTS
Start an arithmetic progression with any two terms from the sequence; the fourth term of that progression is not allowed to be in the sequence.
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..5000
EXAMPLE
Because 0 and 1 are in the sequence, 1 + 2*(1 - 0) = 3 is not in the sequence. Because 5 and 9 are in the sequence, 9 + 2*(9 - 5) = 17 is not in the sequence.
MAPLE
A191767 := proc(n) option remember; local a, k, j; if n <= 2 then n-1 ; else for a from procname(n-1)+1 do atru := true; for j from 1 to n-2 do for k from j+1 to n-1 do if 3*procname(k)-2*procname(j) = a then atru := false; break; end if; end do: if not atru then break; end if; end do: if atru then return a; end if; end do: end if; end proc: # R. J. Mathar, Jun 30 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Weisenhorn, Jun 15 2011
STATUS
approved