A063172 Composite numbers which in base 9 contain their largest proper factor as a substring.

1387, 1849, 2117, 4307, 8299, 34547, 35947, 38491, 68753, 69679, 84281, 90637, 128729, 183097, 185047, 230689, 281443, 407837, 423979, 483029, 664457, 719399, 904537, 1056403, 1121213, 1236511, 1247707, 1303391, 1308947, 1369751

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Mathematica

Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ FromDigits[ IntegerDigits[ n, 9 ] ] ], ToString[ FromDigits[ IntegerDigits[ Divisors[ n ] [ [ -2 ] ], 9 ] ] ] ] != {}, Print[ n ] ], {n, 2, 2*10^6} ]
lpf9Q[n_]:=Module[{idn9=IntegerDigits[n, 9], d9=IntegerDigits[ Divisors[ n][[-2]], 9]}, d9!={1}&&SequenceCount[idn9, d9]>0]; Select[Range[ 2, 1500000], lpf9Q] (* The program uses the SequenceCount function from Mathematica version 10 *) (* Harvey P. Dale, Apr 28 2015 *)

Crossrefs

Cf. A062238.

Sequence in context: A295435 A200315 A063879 * A317972 A216667 A177884

Adjacent sequences: A063169 A063170 A063171 * A063173 A063174 A063175

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 08 2001

Status

approved