A241570 Primes of the form: (concatenation of first n positive integers) - 1.

11, 123456789101112131415161717

Offset

1,1

Comments

Next term, if it exists, has more than 1000 digits.

Links

Table of n, a(n) for n=1..2.

Example

11 in this sequence because 12-1 is prime.

Mathematica

Select[Table[FromDigits[Flatten[IntegerDigits[Range[n]]]] - 1, {n, 1, 100}], PrimeQ] (* after Bruno Berselli *)

Prog

(Magma) c:=0; for d in [1..3] do m:=10^d; for n in [m div 10..m-1] do c:=c*m+n; t:=c-1; if IsPrime(t) then t; end if; end for; end for; // after Jon E. Schoenfield

Crossrefs

Cf. A241569.

Sequence in context: A004022 A243534 A257304 * A083344 A294889 A308425

Adjacent sequences: A241567 A241568 A241569 * A241571 A241572 A241573

Keyword

nonn,base,more,bref

Author

Vincenzo Librandi, Apr 26 2014

Status

approved