OFFSET
1,5
COMMENTS
Numbers n such that Chowla's function(n) = a(n): 1, 2, 3, 10, 15, 28, 75, 88, 231, 284, 602,...
Places n where a(n) is zero: 1, 2, 3, 4, 6, 96,...
Fixed points of this sequence: 17, 53, 127, 217, 385, 2321,...
Places n where a(n) equals the largest anti-divisor: 1, 2, 7, 10, 31, 37, 39, 55, 78, 160, 482, 937, 1599, 2496,...
Numbers n such that n -/+ 1 and a(n -/+ 1) are all primes: 6, 18, 72, 102, 108, 198, 270, 432, 570, 882,...
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
Anti-divisors of 7 are 2, 3, 5, so a(7) = 2 + 3 = 5.
MAPLE
PROG
(PARI) a(n)=if(n<5, 0, my(k=valuation(n, 2)); sigma(2*n+1)+sigma(2*n-1)+sigma(n>>k)<<(k+1)-2-20*n\/3) \\ Charles R Greathouse IV, Mar 05 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Feb 19 2013
STATUS
approved