A075013 Smallest k such that the decimal concatenation of k and k+1 is divisible by n.

1, 1, 1, 1, 4, 1, 5, 5, 4, 9, 16, 1, 7, 5, 4, 19, 3, 13, 22, 19, 16, 27, 2, 19, 24, 7, 31, 5, 31, 19, 27, 19, 16, 3, 9, 31, 26, 41, 7, 19, 28, 37, 20, 27, 4, 51, 20, 19, 16, 49, 52, 35, 32, 31, 49, 5, 22, 31, 66, 19, 32, 27, 58, 19, 9, 49, 6, 35, 28, 9, 26, 67, 13, 63, 49, 79, 16

Offset

1,5

Links

Table of n, a(n) for n=1..77.

Example

a(16) = 19 as 16 divides 1920.

Mathematica

With[{cnct=Table[FromDigits[Flatten[IntegerDigits/@{n, n+1}]], {n, 100}]}, Table[ Position[cnct, _?(Divisible[#, k]&), 1, 1], {k, 100}]]//Flatten (* Harvey P. Dale, Apr 11 2020 *)

Prog

(PARI) for(n=1, 100, k=1:while((k*(10^floor(log(k+1)/log(10)+1))+k+1)%n>0, k=k+1):print1(k", "))

Crossrefs

Cf. A075114, A075115, A075116, A075117.

Sequence in context: A105721 A099310 A021880 * A117379 A007309 A352186

Adjacent sequences: A075010 A075011 A075012 * A075014 A075015 A075016

Keyword

base,nonn

Author

Amarnath Murthy, Sep 01 2002

Extensions

Corrected and extended by Ralf Stephan, Mar 23 2003

Status

approved