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A129476 a(n) is the concatenation in increasing order of all single-digit divisors of n. 1
1, 12, 13, 124, 15, 1236, 17, 1248, 139, 125, 1, 12346, 1, 127, 135, 1248, 1, 12369, 1, 1245, 137, 12, 1, 123468, 15, 12, 139, 1247, 1, 12356, 1, 1248, 13, 12, 157, 123469, 1, 12, 13, 12458, 1, 12367, 1, 124, 1359, 12, 1, 123468, 17, 125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sequence has period 2520 = 2^3 * 3^2 * 5 * 7.

a(n) = 1 iff n is a 11-rough number: not divisible by 2, 3, 5 or 7 (A008364). - Bernard Schott_, Dec 31 2020

LINKS

Michel Marcus, Table of n, a(n) for n = 1..5040

FORMULA

Let n be the rank and result be the number for this rank let a1...ak be k digits (a1...ak in [0,9]) result=a1*10^(k-1)...ak*10^0 with (i|n) => i in {a1...ak}.

EXAMPLE

a(10)=125 because 1, 2 and 5 divides 10. 10 also divides 10 but it is not a digit so it doesn't appear.

a(2520) = 123456789. - Bernard Schott_, Dec 31 2020

MAPLE

a:= n-> parse(cat(seq(`if`(irem(n, i)=0, i, [][]), i=1..9))):

seq(a(n), n=1..50);  # Alois P. Heinz, Dec 31 2020

MATHEMATICA

Table[FromDigits[Select[Divisors[n], #<10&]], {n, 50}] (* Harvey P. Dale, Jun 07 2015 *)

PROG

(PARI) a(n) = fromdigits(select(x->(x<10), divisors(n))); \\ Michel Marcus, Dec 31 2020

(Python)

def a(n): return int('1'+"".join(d for d in "23456789" if n%int(d) == 0))

print([a(n) for n in range(1, 51)]) # Michael S. Branicky, Dec 31 2020

CROSSREFS

Cf. A008364, A037278.

Sequence in context: A058950 A064003 A135123 * A243361 A037278 A164852

Adjacent sequences:  A129473 A129474 A129475 * A129477 A129478 A129479

KEYWORD

nonn,base,easy

AUTHOR

Colin Pitrat (colin.pitrat(AT)rez-gif.supelec.fr), May 29 2007

EXTENSIONS

Editing and comment from Charles R Greathouse IV, Nov 02 2009

More terms from Harvey P. Dale, Jun 07 2015

Name edited by Joerg Arndt, Jan 01 2021

STATUS

approved

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Last modified February 24 13:13 EST 2021. Contains 341569 sequences. (Running on oeis4.)