A216385 Number of values of k for which phi(k) is a permutation of decimal digits of k, for k < 10^n.

1, 3, 5, 21, 78, 403, 2069, 11856, 70835

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Formula

a(n) = # { k in A115921 | k < 10^n }. - M. F. Hasler, Feb 24 2014

Example

a(3) = 5 because the values of k satisfying the condition for k < 10^3 are {1, 21, 63, 291, 502}. - V. Raman, Feb 17 2014

Prog

(PARI) a(n)=sum(k=1, 10^n, vecsort(digits(k)) == vecsort(digits(eulerphi(k)))) \\ Use digits(n)=eval(Vec(Str(n))) in old versions of PARI. - V. Raman, Feb 17 2014, based on edits by M. F. Hasler

Crossrefs

Cf. A115921, A000010.

Sequence in context: A071706 A196418 A189560 * A247680 A179265 A084253

Adjacent sequences: A216382 A216383 A216384 * A216386 A216387 A216388

Keyword

nonn,base,more

Author

V. Raman, Sep 06 2012

Extensions

a(9) from Jinyuan Wang, Mar 03 2020

Status

approved