login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A216392 Number of values of k for which sigma(k) is a permutation of decimal digits of k, for k < 2^n. 0
1, 1, 1, 1, 1, 1, 2, 2, 5, 7, 7, 13, 16, 21, 35, 57, 83, 143, 207, 278, 457, 790, 1064, 1815, 3468, 5194, 8226 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

LINKS

Table of n, a(n) for n=1..27.

FORMULA

a(n) = # { k in A115920 | k < 2^n }. - M. F. Hasler, Feb 24 2014

EXAMPLE

a(10) = 7 because the values of k satisfying the condition for k < 2^10 are {1, 69, 258, 270, 276, 609, 639}. - V. Raman, Feb 18 2014

PROG

(PARI) a(n)=sum(k=1, 2^n, vecsort(digits(k)) == vecsort(digits(sigma(k)))) \\ V. Raman, Feb 18 2014, based on edits by M. F. Hasler

CROSSREFS

Cf. A115920, A000203.

Sequence in context: A207981 A058123 A035586 * A287908 A239259 A188623

Adjacent sequences:  A216389 A216390 A216391 * A216393 A216394 A216395

KEYWORD

nonn,base,more

AUTHOR

V. Raman, Sep 06 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 28 17:19 EDT 2020. Contains 337393 sequences. (Running on oeis4.)