A140494 Numbers that cannot be part of the trajectory of any number under repeated application of the map: n -> n + third-smallest number that does not divide n, unless they are the first term of the trajectory.

1, 2, 3, 4, 6, 12, 18, 24, 28, 30, 36, 37, 40, 42, 46, 48, 49, 52, 54, 55, 60, 64, 66, 72, 78, 80, 84, 88, 90, 96, 97, 100, 102, 106, 108, 112, 114, 115, 120, 124, 126, 132, 133, 138, 144, 150, 156, 157, 160, 162, 166, 168, 172, 174, 175, 180, 184, 186, 192, 198, 200

Offset

1,2

Links

Table of n, a(n) for n=1..61.

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);
canbe(n) = {for (k=1, n, if (k + third(k) == n, return (1)); ); return (0); }
cannotbe(n) = 1 - canbe(n);
lista(nn) = {for (n=1, nn, if (cannotbe(n), print1(n, ", ")); ); } \\ Michel Marcus, Oct 04 2018

Crossrefs

Cf. A140485, A140486, A140487, A140488, A140489 (second-smallest sequences).

Cf. A140490, A140491, A140492, A140493 (third-smallest sequences).

Sequence in context: A296697 A297256 A029952 * A048316 A037393 A048330

Adjacent sequences: A140491 A140492 A140493 * A140495 A140496 A140497

Keyword

nonn

Author

Jacques Tramu, Jun 25 2008

Extensions

Corrected by Michel Marcus, Oct 04 2018

Status

approved