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A140490
Trajectory of 1 under repeated application of the map: n -> n + third-smallest number that does not divide n.
4
1, 5, 9, 14, 19, 23, 27, 32, 38, 43, 47, 51, 56, 62, 67, 71, 75, 81, 86, 91, 95, 99, 104, 110, 116, 122, 127, 131, 135, 141, 146, 151, 155, 159, 164, 170, 176, 182, 187, 191, 195, 201, 206, 211, 215, 219, 224, 230, 236, 242, 247, 251, 255, 261, 266, 271, 275, 279, 284, 290, 296
OFFSET
1,2
COMMENTS
Suggested by Eric Angelini.
LINKS
FORMULA
a(n+12) = a(n) + 60 for n >= 13. - Robert Israel, Jan 17 2023
MAPLE
f:= proc(n) local k, count;
count:= 0;
for k from 2 do
if n mod k <> 0 then count:= count+1; if count = 3 then return n+k fi fi
od
end proc:
R:= 1: x:= 1:
for i from 1 to 100 do x:= f(x); R:= R, x od:
R; # Robert Israel, Jan 17 2023
MATHEMATICA
NestList[#+Complement[Range[#+50], Divisors[#]][[3]]&, 1, 60] (* Harvey P. Dale, Apr 21 2022 *)
PROG
(PARI) third(n) = {my(nb = 0, k = 1); while (nb != 3, if (n % k, nb++); if (nb != 3, k++); ); k; }
f(n) = n + third(n);
lista1(nn) = {a = 1; print1(a, ", "); for (n=2, nn, newa = f(a); print1(newa, ", "); a = f(a); ); } \\ Michel Marcus, Oct 04 2018
CROSSREFS
Cf. A140485, A140486, A140487, A140488, A140489 (second-smallest sequences).
Cf. A140491, A140492, A140493, A140494 (third-smallest sequences).
Sequence in context: A314884 A314885 A314886 * A314887 A316324 A247972
KEYWORD
nonn
AUTHOR
Jacques Tramu, Jun 25 2008
EXTENSIONS
More terms from Michel Marcus, Oct 04 2018
STATUS
approved