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A000422 Concatenation of numbers from n down to 1. 41
1, 21, 321, 4321, 54321, 654321, 7654321, 87654321, 987654321, 10987654321, 1110987654321, 121110987654321, 13121110987654321, 1413121110987654321, 151413121110987654321, 16151413121110987654321, 1716151413121110987654321, 181716151413121110987654321 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The first prime term in this sequence is A000422(82) - Artur Jasinski, Mar 30 2008

REFERENCES

F. Smarandache, "Properties of the Numbers", University of Craiova Archives, 1975; Arizona State University Special Collections, Tempe, AZ

LINKS

T. D. Noe, Table of n, a(n) for n = 1..150

R. W. Stephan, Factors and primes in two Smarandache sequences

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

FORMULA

a(n+1) = (n+1)*10^len(a(n)) + a(n), where len(k) = number of digits in k.

MATHEMATICA

b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[PrependTo[a, w[[Length[w] - k + 1]]], {k, 1, Length[w]}]; p = FromDigits[a]; AppendTo[b, p], {n, 1, 30}]; b - Artur Jasinski, Mar 30 2008

PROG

(PARI) a(n)=my(t=n); forstep(k=n-1, 1, -1, t=t*10^#Str(k)+k); t \\ Charles R Greathouse IV, Jul 15 2011

CROSSREFS

Cf. A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138793.

Sequence in context: A104759 A138793 A014925 * A060554 A057610 A036737

Adjacent sequences:  A000419 A000420 A000421 * A000423 A000424 A000425

KEYWORD

nonn,base

AUTHOR

R. Muller

STATUS

approved

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Last modified September 19 03:51 EDT 2014. Contains 246967 sequences.