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A143421 Number of odd numbers k such that phi(k) = n, where n runs through the values (A002202) taken by phi. 2
1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 3, 1, 1, 1, 3, 3, 2, 1, 1, 2, 1, 1, 1, 1, 4, 1, 1, 1, 6, 1, 2, 1, 2, 2, 1, 4, 2, 1, 1, 1, 4, 1, 2, 1, 6, 1, 1, 1, 3, 1, 1, 1, 5, 1, 1, 3, 2, 2, 1, 1, 4, 1, 2, 1, 5, 1, 1, 4, 1, 1, 3, 1, 1, 1, 1, 7, 2, 1, 2, 1, 1, 2, 1, 10, 1, 4, 1, 1, 1, 3, 1, 1, 2, 4, 3, 1, 6, 1, 1, 1, 2, 1, 1, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

The first zero term is for n = 16842752 = 257*2^16. If there are only five Fermat primes, then terms will be zero for n=2^r for all r>31. This is discussed in problem E3361.

a(2698482) = 0. That is, the 2698482nd term of A002202 is 16842752. - T. D. Noe, Aug 19 2008

REFERENCES

R. K. Guy, Unsolved problems in number theory, B39.

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

T. D. Noe, Numbers Like 16842752

William P. Wardlaw, L. L. Foster and R. J. Simpson, Problem E3361, Amer. Math. Monthly, Vol. 98, No. 5 (May, 1991), 443-444.

FORMULA

A058277(n) = A143421(n) + A143422(n).

CROSSREFS

Sequence in context: A025893 A296977 A025878 * A137672 A141272 A281527

Adjacent sequences:  A143418 A143419 A143420 * A143422 A143423 A143424

KEYWORD

nonn

AUTHOR

T. D. Noe, Aug 14 2008

STATUS

approved

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Last modified June 30 03:34 EDT 2022. Contains 354913 sequences. (Running on oeis4.)