A273281 a(1) = 1, a(n+1) = least multiple of a(n) which is a concatenation in descending order of n+1 successive positive integers.

1, 21, 987, 1602160116001599, 350301931135697350301931135696350301931135695350301931135694350301931135693

Offset

1,2

Comments

In A112364 also 0 is admitted (see a(2) = 10) while in this sequence is not.

Links

Table of n, a(n) for n=1..5.

Example

a(2) / a(1) = 21;
a(3) / a(2) = 47;
a(4) / a(3) = 1623262528877;
a(5) / a(4) = 218643522352760739495083693166843046731892253220075561675507.

Maple

P:=proc(q) local a, b, k, j, n; a:=1; print(a);
for k from 2 to q do for n from 1 to q do
b:=n; for j from 1 to k-1 do b:=(n+j)*10^(ilog10(b)+1)+b; od;
if type(b/a, integer) then a:=b; print(b); break; fi; od; od; end: P(10^9);

Crossrefs

Cf. A112363, A112364.

Sequence in context: A184133 A004704 A138473 * A186392 A360505 A263994

Adjacent sequences: A273278 A273279 A273280 * A273282 A273283 A273284

Keyword

nonn,base

Author

Paolo P. Lava, May 19 2016

Extensions

a(5) from Giovanni Resta, May 19 2016

Status

approved