A322097 a(1)=1, a(2)=1; for n > 2, a(n) is the largest proper divisor of the concatenation of terms a(1) through a(n-1).

1, 1, 1, 37, 1591, 3010043, 159102273287149, 65512700765296656417780781597, 37123863767001438636742442904988504233588432218805926927199, 3712386376700143863674244290498850423358843221880592692719912374621255667146212247480968329501411196144072935308975733

Offset

1,4

Comments

This sequence is nondecreasing. Indeed, let c(n) be the concatenation of the first n terms of this sequence and d(n) the number of decimal digits of a(n). For n > 2, a(n) divides c(n-1), so a(n) is a proper divisor of c(n-1)*10^d(n) + a(n) = c(n), and thus a(n) <= a(n+1). - Danny Rorabaugh, Nov 27 2018

a(11) is too large to show in the Data section. It is

3712386376700143863674244290498850423358843221880592692719912374621255667\

1462122474809683295014111961440729353089757331237462125566714621224748096\

8329501411196144072935308975733041248737518890487374158269894431671370653\

81357645102991911.

Links

Table of n, a(n) for n=1..10.

Mathematica

FromDigits /@ Nest[Append[#, IntegerDigits@ Divisors[FromDigits[Join @@ #]][[-2]] ] &, {{1}, {1}}, 8] (* Michael De Vlieger, Nov 26 2018 *)

Crossrefs

Cf. A322098.

Sequence in context: A279330 A009695 A201956 * A260667 A130013 A370149

Adjacent sequences: A322094 A322095 A322096 * A322098 A322099 A322100

Keyword

nonn,base

Author

John Mason, Nov 26 2018

Status

approved