A140488 Trajectory of 5 under repeated application of the map: n -> n + second-smallest number that does not divide n.

5, 8, 13, 16, 21, 25, 28, 33, 37, 40, 46, 50, 54, 59, 62, 66, 71, 74, 78, 83, 86, 90, 97, 100, 106, 110, 114, 119, 122, 126, 131, 134, 138, 143, 146, 150, 157, 160, 166, 170, 174, 179, 182, 186, 191, 194, 198, 203, 206, 210, 218, 222, 227, 230, 234, 239, 242, 246

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

It appears that a(n+98) = a(n)+420 for n >= 9. - Robert Israel, Oct 19 2021

Maple

f:= proc(n) local k, c;
c:= 0:
for k from 2 do
  if n mod k <> 0 then
    if c = 1 then return n+k fi;
    c:= 1;
  fi
od
end proc:
R:= 5: t:= 5:
for count from 2 to 100 do
  t:= f(t);
  R:= R, t;
od:
R; # Robert Israel, Oct 19 2021

Mathematica

a = {5}; Do[AppendTo[a, a[[ -1]] + Select[Range[a[[ -1]]], Mod[a[[ -1]], # ] > 0 &][[2]]], {60}]; a (* Stefan Steinerberger, Jul 01 2008 *)

Prog

(Python)
def aupton(terms):
    alst = [5]
    while len(alst) < terms:
        an, k, smallest = alst[-1], 2, False
        while not smallest or an%k == 0:
            if not smallest and an%k != 0: smallest = True
            k += 1
        alst.append(an+k)
    return alst
print(aupton(58)) # Michael S. Branicky, Oct 19 2021

Crossrefs

Cf. A140485, A140486, A140487, A140489.

Sequence in context: A047615 A314421 A314422 * A314423 A314424 A314425

Adjacent sequences: A140485 A140486 A140487 * A140489 A140490 A140491

Keyword

nonn

Author

Eric Angelini, Jun 25 2008

Extensions

Corrected and extended by Stefan Steinerberger, Jul 01 2008

Status

approved