A062238 -id:A062238 - cp's OEIS frontend

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

Robert G. Wilson v, Aug 08 2001

Cf. A062238.

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 *)

A063139 Composite numbers which in base 3 contain their largest proper factor as a substring.

Original entry on oeis.org

9, 15, 21, 27, 33, 39, 45, 49, 51, 57, 63, 69, 75, 81, 87, 93, 99, 105, 111, 117, 123, 129, 135, 141, 147, 153, 159, 165, 171, 177, 183, 189, 195, 201, 207, 213, 219, 225, 231, 237, 243, 249, 255, 261, 267, 273, 279, 285, 291, 297

Offset: 1

Robert G. Wilson v, Aug 08 2001

Cf. A062238.

Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ FromDigits[ IntegerDigits[ n, 3 ] ] ], ToString[ FromDigits[ IntegerDigits[ Divisors[ n ] [ [ -2 ] ], 3 ] ] ] ] != {}, Print[ n ] ], {n, 2, 10^2} ]

A063248 Smallest composite number in base n which contains its largest proper factor as a substring.

Original entry on oeis.org

4, 9, 407, 25, 9, 49, 893, 1387, 15, 121, 23533, 169, 21, 4717, 10579, 289, 27, 361, 25, 49, 33, 529, 32437, 61903, 39, 24523, 35, 841, 45, 961, 39917, 77, 51, 64993, 111277, 1369, 57, 91, 99101, 1681, 49, 1849, 55, 108389, 69, 2209, 207133, 139163

Offset: 2

Robert G. Wilson v, Aug 08 2001

Cf. A062238.

sublist[ s_, l_ ] := Module[ {i, ls=Length[ s ]}, For[ i=1, i+ls-1<=Length[ l ], i++, If[ s==Take[ l, {i, i+ls-1} ], Return[ True ] ] ]; False ]; a[ n_ ] := Module[ {k}, For[ k=4, True, k++, If[ !PrimeQ[ k ]&&sublist[ IntegerDigits[ Divisors[ k ][ [ -2 ] ], n ], IntegerDigits[ k, n ] ], Return[ k ] ] ] ];

More terms from Dean Hickerson, Aug 10 2001

cp's OEIS Frontend

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

Views

Author

Keywords

Crossrefs

Programs

Mathematica

A063139 Composite numbers which in base 3 contain their largest proper factor as a substring.

Views

Author

Keywords

Crossrefs

Programs

Mathematica

A063248 Smallest composite number in base n which contains its largest proper factor as a substring.

Views

Author

Keywords

Crossrefs

Programs

Mathematica

Extensions