login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A164323 Numbers n such that n=prime(P)+phi(P), where P is the product of the digits of n. 2
15, 383, 629, 8297 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The product of the digits of next term (if it exists) is greater than 2*10^8.

The sequence is finite since prime(P) ~= P*log(P) and phi(P) < P, while n > 10^(log(P)/log(9)) - 1 > P^1.047. [From Max Alekseyev]

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

8297=prime(8*2*9*7)+phi(8*2*9*7), so 8297 is in the sequence.

MATHEMATICA

Do[If[n=Prime[m]+Eulerphi[m]; m==Apply[Times, IntegerDigits[n]], Print[n]],

{m, 200000000}]

CROSSREFS

Cf. A000040, A000010, A164322, A164324.

Sequence in context: A035274 A324415 A145409 * A129615 A286139 A069990

Adjacent sequences:  A164320 A164321 A164322 * A164324 A164325 A164326

KEYWORD

base,more,nonn,fini

AUTHOR

Farideh Firoozbakht, Aug 13 2009

EXTENSIONS

Keyword fini added by Max Alekseyev, Dec 14 2011

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 May 21 08:52 EDT 2019. Contains 323441 sequences. (Running on oeis4.)