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A163822 Number of divisors d of 2n such that gcd(d-1,2n/d-1) = 1. 2
2, 1, 2, 2, 2, 4, 2, 2, 4, 4, 2, 6, 2, 2, 6, 4, 2, 6, 2, 4, 6, 4, 2, 8, 4, 2, 6, 6, 2, 10, 2, 2, 4, 4, 4, 10, 2, 2, 6, 8, 2, 10, 2, 4, 10, 4, 2, 8, 4, 4, 6, 6, 2, 10, 6, 4, 6, 4, 2, 12, 2, 2, 8, 6, 4, 10, 2, 4, 6, 10, 2, 12, 2, 2, 10, 6, 4, 8, 2, 6, 8, 4, 2, 14, 6, 2, 6, 4, 2, 16, 6, 4, 4, 4, 4, 12, 2, 2, 10 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The corresponding values for odd n are all zero, since then 2 is a common divisor of (d-1,n/d-1).
LINKS
PROG
(PARI) a(n)=local(d, r); r=0; d=divisors(2*n); for(k=1, #d, if(gcd(d[k]-1, 2*n\d[k]-1)==1, r++)); r
CROSSREFS
Sequence in context: A079526 A353339 A291708 * A029203 A363526 A159805
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified March 19 04:26 EDT 2024. Contains 370952 sequences. (Running on oeis4.)