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 A332810 Number of integers in range 1..n that are not encountered on any of the possible paths from n to 1 when iterating with nondeterministic map k -> k - k/p, where p is any prime factor of k. 4

%I #12 Apr 08 2020 02:27:39

%S 0,0,0,1,1,1,1,4,3,4,4,5,5,5,5,11,11,9,9,12,9,12,12,15,16,15,17,16,16,

%T 16,16,26,16,26,17,24,24,24,24,30,30,25,25,31,27,31,31,37,31,38,37,38,

%U 38,40,39,41,40,41,41,42,42,42,43,57,43,43,43,58,43,46,46,57,57,57,54,58,47,58,58,68,66,68,68,62,69,62,62,72,72

%N Number of integers in range 1..n that are not encountered on any of the possible paths from n to 1 when iterating with nondeterministic map k -> k - k/p, where p is any prime factor of k.

%H Antti Karttunen, <a href="/A332810/b332810.txt">Table of n, a(n) for n = 1..20000</a>

%F a(n) = n - A332809(n).

%e a(12): we have three alternative paths: {12, 8, 4, 2, 1}, {12, 6, 4, 2, 1} or {12, 6, 3, 2, 1}, with [5, 7, 9, 10, 11] being the only numbers in range 1..12 that do not occur in any of those paths, therefore a(12) = 5.

%o (PARI)

%o up_to = 105;

%o A332809list(up_to) = { my(v=vector(up_to)); v[1] = Set([1]); for(n=2,up_to, my(f=factor(n)[, 1]~, s=Set([n])); for(i=1,#f,s = setunion(s,v[n-(n/f[i])])); v[n] = s); apply(length,v); }

%o v332809 = A332809list(up_to);

%o A332810(n) = (n-v332809[n]);

%Y Cf. A064097, A332809, A333123.

%K nonn

%O 1,8

%A _Antti Karttunen_, Apr 04 2020

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Last modified April 18 10:46 EDT 2024. Contains 371779 sequences. (Running on oeis4.)