The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A209930 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A209930

Numbers n such that largest digit of all divisors of n is 1.
(history; published version)

#16 by N. J. A. Sloane at Wed Jul 16 15:34:53 EDT 2014

STATUS

proposed

approved

#15 by Alois P. Heinz at Wed Jul 16 14:50:36 EDT 2014

STATUS

editing

proposed

#14 by Alois P. Heinz at Wed Jul 16 14:49:32 EDT 2014

LINKS

Alois P. Heinz, <a href="/A209930/b209930.txt">Table of n, a(n) for n = 1..8503</a>

#13 by Alois P. Heinz at Wed Jul 16 10:36:59 EDT 2014

COMMENTS

What is the smallest n with a(n) <> A203304(n)? - Alois P. Heinz, Jul 16 2014

STATUS

proposed

editing

#12 by Alois P. Heinz at Tue Jul 15 21:32:40 EDT 2014

STATUS

editing

proposed

Discussion

Tue Jul 15

22:57

Franklin T. Adams-Watters: I suspect that it is not a duplicate. One wants to show that multiplying the factors, there are no carries. To get a contradiction to that, you would need two primes with at least 10 1's each (rest 0's), such that you get 10 contributions to the same digit, and all others are 0's and 1's. If one of those bit-wise products includes the units digit of one of the numbers, then phi of that product would have a digit 8 or 9. But such an exception would be very large.

#11 by Alois P. Heinz at Tue Jul 15 21:30:57 EDT 2014

CROSSREFS

Cf. A203304.

#10 by Alois P. Heinz at Tue Jul 15 21:27:51 EDT 2014

EXTENSIONS

Corrected by _Jaroslav Krizek, _, Jan 29 2013

STATUS

approved

editing

Discussion

Tue Jul 15

21:28

Alois P. Heinz: This seems to be a duplicate of A203304.

#9 by T. D. Noe at Wed Jan 30 13:23:29 EST 2013

STATUS

editing

approved

#8 by T. D. Noe at Wed Jan 30 13:22:24 EST 2013

DATA

1, 11, 101, 1111, 10111, 101111, 1011001, 1100101, 10010101, 10011101, 10100011, 10101101, 10110011, 10111001, 11000111, 11100101, 11110111, 11111101, 100100111, 100111001, 101001001, 101001011, 101100011, 101101111, 101111011, 101111111, 110010101

MATHEMATICA

t = {}; n = 0; While[Length[t] < 30, n++; m = FromDigits[IntegerDigits[n, 2]]; If[Max[Union[Flatten[IntegerDigits[Divisors[m]]]]] <= 1, AppendTo[t, m]]]; t (* T. D. Noe, Jan 30 2013 *)

EXTENSIONS

Corrected by Jaroslav Krizek, Jan 29 2013

STATUS

proposed

editing

#7 by Jaroslav Krizek at Mon Jan 28 19:01:52 EST 2013

STATUS

editing

proposed