login
A374204
a(n) is the minimum value of A347381 that it obtains among divisors of n larger than 1. By convention a(1) = 0.
7
0, 0, 1, 0, 1, 0, 3, 0, 1, 0, 3, 0, 2, 0, 1, 0, 6, 0, 5, 0, 1, 0, 7, 0, 1, 0, 1, 0, 8, 0, 10, 0, 1, 0, 1, 0, 4, 0, 1, 0, 10, 0, 9, 0, 1, 0, 13, 0, 3, 0, 1, 0, 15, 0, 1, 0, 1, 0, 15, 0, 7, 0, 1, 0, 1, 0, 12, 0, 1, 0, 19, 0, 9, 0, 1, 0, 3, 0, 19, 0, 1, 0, 20, 0, 1, 0, 1, 0, 22, 0, 2, 0, 1, 0, 1, 0, 24, 0, 1, 0, 20
OFFSET
1,7
FORMULA
a(1) = 0, and for n > 1, a(n) = Min_{d|n, d>1} A347381(d).
For nonprime n, a(n) = min(A347381(n), A374214(n)).
PROG
(PARI)
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1, 1]==2), f[1, 2] = 0); for (i=1, #f~, f[i, 1] = precprime(f[i, 1]-1)); factorback(f)};
A252463(n) = if(!(n%2), n/2, A064989(n));
A347381(n) = if(1==n, 0, my(lista=List([]), i, k=n, stemvec, stemlen, sbr=sigma(n)); while(k>1, listput(lista, k); k = A252463(k)); stemvec = Vecrev(Vec(lista)); stemlen = #stemvec; while(1, if((i=vecsearch(stemvec, sbr))>0, return(stemlen-i)); sbr = A252463(sbr)));
A374204(n) = { my(m=-1, x); fordiv(n, d, if(d>1, x = A347381(d); if(m<0 || x<m, m=x))); if(-1==m, 0, m); };
CROSSREFS
Cf. also A374196.
Sequence in context: A109718 A053385 A213543 * A247254 A035640 A079327
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 07 2024
STATUS
approved