A340594 a(n) is the number of iterations of A340592 starting from n, until 0, 1 or a prime is reached.

0, 0, 1, 0, 1, 0, 2, 2, 1, 0, 1, 0, 1, 1, 2, 0, 1, 0, 1, 3, 1, 0, 2, 1, 1, 3, 1, 0, 2, 0, 2, 2, 1, 2, 1, 0, 1, 1, 2, 0, 4, 0, 1, 2, 2, 0, 1, 2, 1, 1, 1, 0, 1, 3, 1, 2, 4, 0, 2, 0, 3, 2, 2, 5, 1, 0, 1, 1, 1, 0, 3, 0, 2, 4, 2, 2, 2, 0, 6, 2, 3, 0, 1, 1, 1, 2, 3, 0, 2, 3, 2, 2, 1, 2, 1, 0, 3, 2

Offset

2,7

Comments

a(n) = 0 if n is prime.

Links

Robert Israel, Table of n, a(n) for n = 2..10000

Formula

a(n) = A066247(n)*(1 + a(A340592(n))).

Example

A340592(21) = 16, A340592(16) = 14, A340592(14) = 13 is prime, so a(21) = 3.

Maple

dcat:= proc(L) local i, x;
  x:= L[-1];
  for i from nops(L)-1 to 1 by -1 do
    x:= 10^(1+ilog10(x))*L[i]+x
  od;
  x
end proc:
f:= proc(n) local F;
  F:= sort(ifactors(n)[2], (a, b) -> a[1] < b[1]);
  dcat(map(t -> t[1]$t[2], F)) mod n;
end proc:
g:= proc(n) option remember;
     if isprime(n) then 0 else 1 + procname(f(n)) fi
end proc:
g(0):= 0: g(1):= 0:
map(g, [$1..1000]);

Crossrefs

Cf. A066247, A340592, A340595.

Sequence in context: A368579 A287331 A179769 * A361685 A227193 A287397

Adjacent sequences: A340591 A340592 A340593 * A340595 A340596 A340597

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Jan 13 2021

Status

approved