A324825 Number of divisors d of n such that A323243(d) is odd; number of terms of A324813 larger than 1 that divide n.
0, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 2, 1, 2, 2, 1, 1, 2, 1, 3, 3, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 1, 2, 2, 2, 2, 1, 2, 2, 3, 1, 4, 1, 2, 2, 2, 1, 2, 1, 4, 2, 2, 1, 2, 3, 2, 2, 2, 1, 4, 1, 2, 3, 1, 2, 3, 1, 2, 2, 4, 1, 2, 1, 2, 2, 2, 2, 3, 1, 3, 1, 2, 1, 4, 2, 2, 2, 2, 1, 4, 3, 2, 2, 2, 2, 2, 1, 3, 2, 4, 1, 3, 1, 2, 4
Offset: 1
Keywords
Links
Programs
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PARI
A156552(n) = {my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res}; \\ From A156552 by David A. Corneth A324823(n) = if(1==n,0, n=A156552(n); (issquare(n) || (!(n%2) && issquare(n/2)))); A324825(n) = sumdiv(n,d,A324823(d));
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PARI
A324825(n) = sumdiv(n,d,A323243(d)%2); \\ This needs code also from A323243.
Formula
a(n) = Sum_{d|n} A324823(d).
a(p^k) = 1, for all primes p and exponents k >= 1.
Comments