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A347244
Characteristic function of A347242.
7
0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1
OFFSET
1
FORMULA
a(1) = 0, and for n > 1, a(n) = 1 if for some k > 0, A006530(A000593^(k)(n)) >= A006530(n), otherwise 0. Here A000593^(k) means the k-fold application of the sum of odd divisors.
For n >= 1, a(n) = 0 iff A347245(n) = 0.
PROG
(PARI)
A000265(n) = (n >> valuation(n, 2));
A000593(n) = sigma(A000265(n));
A006530(n) = if(1==n, n, my(f=factor(n)); f[#f~, 1]);
A347244(n) = { my(gpf=A006530(n)); while(n>1, n = A000593(n); if(A006530(n)>=gpf, return(1))); (0); };
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 28 2021
STATUS
approved