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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: A136192 A118431 A051809 * A120876 A216073 A086870

Adjacent sequences:  A034051 A034052 A034053 * A034055 A034056 A034057

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Sep 15 1998.

STATUS

approved

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Last modified April 20 13:42 EDT 2014. Contains 240806 sequences.