A079791 a(1) = 1, a(n) = a(n-1)/n if a(n-1) is divisible by n else a(n) is the concatenation of a(n-1) and n.

1, 12, 4, 1, 15, 156, 1567, 15678, 1742, 174210, 17421011, 1742101112, 174210111213, 17421011121314, 1742101112131415, 174210111213141516, 17421011121314151617, 1742101112131415161718, 174210111213141516171819

Offset

1,2

Comments

After 9, the next time a(n-1) is divisible by n is n = 703. - Robert Israel, Dec 03 2024

Links

Robert Israel, Table of n, a(n) for n = 1..370

Example

a(3) = 12/3 = 4 a(4) = 4/4 = 1, a(5) = 15.

Maple

A[1]:= 1:
for n from 2 to 50 do
  if A[n-1] mod n = 0 then A[n]:= A[n-1]/n else A[n]:= tcat(A[n-1], n) fi;
od:
convert(A, list); # Robert Israel, Dec 03 2024

Mathematica

Transpose[NestList[{#[[1]]+1, If[Divisible[#[[2]], #[[1]]+1], #[[2]]/ (#[[1]]+ 1), FromDigits[Flatten[Join[IntegerDigits[#[[2]]], IntegerDigits[ #[[1]]+ 1]]]]]}&, {1, 1}, 20]][[2]] (* Harvey P. Dale, Apr 25 2012 *)

Prog

(PARI) f=1; for(i=1, 40, if(f%i==0, f=f/i, f=eval(concat(Str(f), i))); print1(f, ", ")) \\ Lambert Herrgesell (zero815(AT)googlemail.com), Mar 13 2006

Crossrefs

Sequence in context: A261403 A010202 A079792 * A018812 A306375 A139358

Adjacent sequences: A079788 A079789 A079790 * A079792 A079793 A079794

Keyword

base,nonn

Author

Amarnath Murthy, Feb 04 2003

Extensions

More terms from Lambert Herrgesell (zero815(AT)googlemail.com), Mar 13 2006

Status

approved