A173660 Smallest integer not yet present such that [a(n)+a(n+1)] divides the concatenation [a(n),a(n+1)].

1, 2, 4, 5, 10, 8, 14, 7, 26, 13, 20, 16, 17, 34, 32, 12, 6, 3, 24, 30, 15, 18, 9, 72, 27, 54, 45, 36, 63, 126, 28, 35, 42, 21, 56, 43, 86, 136, 51, 48, 40, 50, 25, 74, 37, 62, 31, 68, 64, 80, 19, 38, 61, 122, 76, 23, 46, 53, 106, 92, 115, 218, 109, 224, 84

Offset

1,2

References

Posting by Eric Angelini to Sequence Fans Mailing List, Sep 21 2010

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000

Example

1+2 divides 12    ->  12/3=4
2+4 divides 24    ->  24/6=4
4+5 divides 45    ->  45/9=5
5+10 divides 510  -> 510/15=34
10+8 divides 108  -> 108/18=6
8+14 divides 814  -> 814/22=37
...

Maple

ina:= proc() false end:
ina(1):= true: mina:= 2;
a:= proc(n) option remember; global mina; local k;
      if n=1 then 1
    else for k from mina while ina(k) or
           irem(parse(cat(a(n-1), k)), a(n-1)+k)<>0 do od;
         ina(k):= true; while ina(mina) do mina:= mina+1 od;
         k
      fi
    end:
seq(a(n), n=1..70);  # Alois P. Heinz, Sep 30 2011

Crossrefs

Sequence in context: A125728 A351871 A276608 * A353384 A335315 A307805

Adjacent sequences: A173657 A173658 A173659 * A173661 A173662 A173663

Keyword

nonn,base

Author

N. J. A. Sloane, Nov 24 2010

Extensions

Corrected and extended by Alois P. Heinz, Sep 30 2011

Status

approved