A279535 Triangle read by rows: The number of digits in the smallest 9-repdigit that is a multiple of n and m, where n and m are coprime to 2 and 5.

1, 1, 1, 6, 6, 42, 1, 3, 6, 9, 2, 2, 6, 2, 22, 6, 6, 6, 6, 6, 78, 16, 16, 48, 16, 16, 48, 272, 18, 18, 18, 18, 18, 18, 144, 342, 6, 6, 42, 6, 6, 6, 48, 18, 42, 22, 22, 66, 22, 22, 66, 176, 198, 66, 506, 3, 9, 6, 27, 6, 6, 48, 18, 18, 66, 81, 28, 28, 84, 28, 28, 84, 112, 252, 84, 308, 84, 812

Offset

1,4

Comments

The number of digits of the smallest member of A002283 divisible by n and m, as n and m run through A045572. Numbers of the form 10^d-1 are not divisible through 5 or 2, so these are excluded in the table. Losely related to A278588.

Links

Table of n, a(n) for n=1..78.

Formula

T(i,j) = min{d: (n*m) | (10^d-1)} where n=A045572(i) and m=A045572(j).

Example

The 3rd smallest number coprime to 2 and 5 is A045572(3)=7. The smallest 9-repdigit divisible by 7*7=49 is 10^42-1 = A002283(42), to T(3,3)=42.
The triangle starts
   1;
   1,  1;
   6,  6, 42;
   1,  3,  6,  9;
   2,  2,  6,  2, 22;
   6,  6,  6,  6,  6, 78;
  16, 16, 48, 16, 16, 48, 272;

Crossrefs

Cf. A002283, A002329, A045572

Sequence in context: A278435 A279333 A278734 * A125510 A117859 A229159

Adjacent sequences: A279532 A279533 A279534 * A279536 A279537 A279538

Keyword

nonn,tabl,base

Author

R. J. Mathar, Dec 14 2016

Status

approved