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A069863 a(n) is the shortest concatenation of two or more decreasing consecutive numbers (n)(n-1)...(0) such that n divides a(n), or n if there is no such concatenation. 0
10, 210, 321, 432, 543210, 654, 7, 8765432, 987654321, 109876543210, 11, 1211109876, 13, 14131211109876, 151413121110, 1615141312, 171615, 181716151413121110, 19181716, 20, 21, 2221201918171615141312, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = n for the following values of n: 7, 11, 13, 20, 21, 23, 25, 26, 29, 31, 37, 38, 39, 50, 52, 53, 58, 59, 62, 63, 65, 67, 71, 74, 81, 82, 85, 89, 91, 92, 95, 97, 100, 101, 106, 115, 116, 118, 130, 133, 145, 146, 152, 159, 169, 173, 175, 178, 182, 184, 185, 195, 196, 200, 212, 213, 214, 215, 217, 220, 221, 224, 227, 229, 230, 232, 235, 236, 239, 243, 250, ...

LINKS

Table of n, a(n) for n=1..23.

EXAMPLE

a(7) = 7 the corresponding k = 0, a(2) =210, k=2. a(4) = 432, k = 2.

MATHEMATICA

f[n_] := Block[{j = n, k = n - 1}, While[j = ToExpression[ StringJoin[ ToString[j], ToString[k]]]; !IntegerQ[j/n] && k > -1, k-- ]; If[k == -1, Return[n], Return[j]]]; Table[f[n], {n, 1, 30}]

CROSSREFS

Cf. A069860, A069861, A069862.

Sequence in context: A245918 A211107 A215555 * A160476 A067642 A052245

Adjacent sequences:  A069860 A069861 A069862 * A069864 A069865 A069866

KEYWORD

base,nonn,less

AUTHOR

Amarnath Murthy, Apr 18 2002

EXTENSIONS

Edited by Robert G. Wilson v, Apr 22 2002

Edited by T. D. Noe, Apr 09 2009

STATUS

approved

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Last modified October 15 00:12 EDT 2019. Contains 328025 sequences. (Running on oeis4.)