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A056692
Number of divisors k of n with gcd(k-1, n) = 1.
1
1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 3, 1, 2, 3, 4, 1, 3, 1, 4, 2, 2, 1, 5, 2, 2, 3, 4, 1, 2, 1, 5, 3, 2, 3, 5, 1, 2, 2, 6, 1, 4, 1, 4, 5, 2, 1, 6, 2, 3, 3, 4, 1, 4, 2, 5, 2, 2, 1, 5, 1, 2, 4, 6, 3, 3, 1, 4, 3, 4, 1, 8, 1, 2, 4, 4, 3, 4, 1, 7, 4, 2, 1, 6, 3, 2, 3, 6, 1, 4, 3, 4, 2, 2, 3, 8, 1, 3, 5, 6, 1, 3, 1, 6, 4
OFFSET
1,4
LINKS
EXAMPLE
The positive divisors of 8 are 1, 2, 4, 8. (2-1), (4-1) and (8-1) are relatively prime to 8, so a(8) = 3.
MATHEMATICA
Table[DivisorSum[n, 1 &, CoprimeQ[# - 1, n] &], {n, 105}] (* Michael De Vlieger, Oct 30 2017 *)
PROG
(PARI) A056692(n) = sumdiv(n, d, (1==gcd(d-1, n))); \\ Antti Karttunen, Oct 30 2017
CROSSREFS
Sequence in context: A318473 A127669 A323436 * A331600 A039637 A194548
KEYWORD
nonn
AUTHOR
Leroy Quet, Aug 10 2000
STATUS
approved