OFFSET
1,1
COMMENTS
Start with the list of positive integers.
Call the current version of the list b(1), b(2), b(3), ...
Remove b(1) = 1 and renumber the terms.
Remove b(2) and b(2+1) from the remaining list and renumber the terms.
Remove b(3), b(3+2) and b(3+2+1) from the remaining list and renumber the terms.
Remove b(4), b(4+3), b(4+3+2) and b(4+3+2+1) from the remaining list and renumber the terms.
Repeat the process. What is left forms the sequence.
LINKS
Austin C. Green and T. D. Noe, Table of n, a(n) for n=1..1000 (b-file extended and corrected).
EXAMPLE
a(3) = 7 because:
integer 1 is eliminated in the first round,
integers 3 and 4 are eliminated in the second round and
integers 6, 8 and 9 are eliminated in the third round.
This leaves the numbers 2, 5, 7...
MATHEMATICA
lg = 1000; max = (lg+1)^2; Clear[p, bb, n]; p[1] = {{1}}; p[n_] := p[n] = Prepend[p[n-1]+n, {n}]; bb[n_] := bb[n] = Delete[bb[n-1], p[n]]; bb[0] = Range[max]; bb[n=1]; While[n <= lg && bb[n][[;; lg]] != bb[n-1][[;; lg]], n++]; A133436 = bb[n][[;; lg]] (* Jean-François Alcover, Mar 24 2016 *)
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Austin C. Green (whyphi(AT)gmail.com), Nov 25 2007
STATUS
approved