

A007923


Lengths increase by 1, digits cycle through positive digits.


7



1, 23, 456, 7891, 23456, 789123, 4567891, 23456789, 123456789, 1234567891, 23456789123, 456789123456, 7891234567891, 23456789123456, 789123456789123, 4567891234567891, 23456789123456789, 123456789123456789
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OFFSET

1,2


REFERENCES

C. Ashbacher, Some Problems Concerning the Smarandache Deconstructive Sequence, J. Recreational Mathematics, Vol. 29, No. 2, pages 8284.
K. Atanassov, On the 4th Smarandache Problem, Notes on Number Theory and Discrete Mathematics, Sophia, Bulgaria, Vol. 5 (1999), No. 1, 3335.


LINKS

John Cerkan, Table of n, a(n) for n = 1..994
K. Atanassov, On Some of Smarandache's Problems
F. Smarandache, Only Problems, Not Solutions!
Eric Weisstein's World of Mathematics, Smarandache Sequences


FORMULA

a(n) = (10^9+1) a(n9)  10^9 a(n18), n>=18.  corrected by Michael Somos, Sep 28 2002
a(n) = Sum_{i=1..n} ((n*(n1)/2+i1 mod 9)+1)*10^(ni).  Vedran Glisic, Apr 08 2011
a(n) = floor(10^(n*(n+1)/2)*123456789/999999999)  10^n*floor(10^(n*(n1)/2)*123456789/999999999).  Néstor Jofré, Jun 03 2017


PROG

(PARI) a(n)=my(m=(n*(n+1)/21)%9); sum(k=0, n1, 10^k*((mk)%9+1))


CROSSREFS

Cf. A001369, A007924, A050234, A066547.
Sequence in context: A062273 A066547 A001369 * A080479 A053067 A036906
Adjacent sequences: A007920 A007921 A007922 * A007924 A007925 A007926


KEYWORD

nonn,easy,base


AUTHOR

R. Muller


STATUS

approved



