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

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A034054 Numbers with multiplicative digital root value 7. 13
7, 17, 71, 117, 171, 711, 1117, 1171, 1711, 7111, 11117, 11171, 11711, 17111, 71111, 111117, 111171, 111711, 117111, 171111, 711111, 1111117, 1111171, 1111711, 1117111, 1171111, 1711111, 7111111, 11111117, 11111171, 11111711, 11117111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers with one 7, and zero or more 1s. - Daniel Forgues, Oct 09 2011

LINKS

Table of n, a(n) for n=1..32.

Eric Weisstein's World of Mathematics, Multiplicative Digital Root

FORMULA

There are n(n+1)/2 elements up to 10^n, so a(n) is about 10^sqrt(2n).

CROSSREFS

Cf. A031347.

Cf. A034048, A002275, A034049, A034050, A034051, A034052, A034053, A034054, A034055, A034056 (numbers having multiplicative digital roots 0-9).

Sequence in context: A118431 A051809 A242907 * A120876 A216073 A086870

Adjacent sequences:  A034051 A034052 A034053 * A034055 A034056 A034057

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Sep 15 1998.

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified December 19 19:12 EST 2014. Contains 252239 sequences.