A351258 a(n) = A099307(A351255(n)) - A051903(A351255(n)).

1, 1, 1, 2, 2, 3, 1, 2, 2, 2, 3, 3, 2, 2, 1, 4, 3, 2, 2, 2, 2, 2, 3, 2, 2, 4, 9, 4, 5, 2, 2, 2, 2, 2, 2, 2, 2, 4, 4, 2, 2, 9, 2, 2, 2, 5, 6, 2, 2, 2, 3, 2, 2, 2, 2, 6, 2, 6, 1, 2, 5, 2, 2, 2, 2, 3, 2, 2, 2, 5, 2, 2, 2, 8, 5, 2, 2, 6, 2, 2, 9, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 6, 2, 3, 7, 3, 3, 3, 4, 2, 2, 3, 2, 8

Offset

1,4

Comments

All terms are > 0 because from any k > 0, one certainly cannot reach 1 in less than A051903(k) iterations of the map x -> A003415(x).

One of the records occur at a(20457) = 38. The corresponding term of A351255 is A351255(20457) = A276086(A328116(20457)) = A276086(688352) = 442600020398400142264711707660915237 = 3 * 7^6 * 11^10 * 13^11 * 17^5 * 19. When starting iterating from this value with A003415, it first goes relatively smoothly in 11 steps to the first squarefree number encountered, 6201461846617177861789236821121654153, but after that, it still meanders for the additional 37 iterations (visiting mostly squarefree numbers, but also six numbers with max. exponent = 2, and one number with max. exponent = 3), before finally reaching zero.

Links

Antti Karttunen, Table of n, a(n) for n = 1..105368 (computed for all 19-smooth terms of A351255, and also for A276086(9699690) = 23)

Formula

a(n) = A351257(n) - A351256(n) = A099307(A351255(n)) - A051903(A351255(n)).

Prog

(PARI)
A003415checked(n) = if(n<=1, 0, my(f=factor(n), s=0); for(i=1, #f~, if(f[i, 2]>=f[i, 1], return(0), s += f[i, 2]/f[i, 1])); (n*s));
A051903(n) = if((1==n), 0, vecmax(factor(n)[, 2]));
A099307(n) = { my(s=1); while(n>1, n = A003415checked(n); s++); if(n, s, 0); };
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
for(n=0, 2^9, u=A276086(n); c = A099307(u); if(c>0, print1(c-A051903(u), ", ")));

Crossrefs

Cf. A003415, A051903, A099307, A351255, A351256, A351257.

Sequence in context: A330155 A327759 A269978 * A097028 A289442 A092331

Adjacent sequences: A351255 A351256 A351257 * A351259 A351260 A351261

Keyword

nonn

Author

Antti Karttunen, Feb 11 2022

Status

approved