A092025 Numbers k such that the concatenation of the first k positive integers plus prime(k) is prime.

1, 44, 66, 398, 1582, 2484

Offset

1,2

Comments

For n > 1, a(n) is even.

a(7) > 20239. - J.W.L. (Jan) Eerland, Mar 03 2023

Links

Table of n, a(n) for n=1..6.

Example

66 is in the sequence because 1.2.3...65.66 + prime(66) is prime.

Mathematica

n=1; Monitor[Parallelize[While[True, If[PrimeQ[Prime[n]+FromDigits[Join@@IntegerDigits/@Range[n]]], Print[n]]; n++]; n], n] (* J.W.L. (Jan) Eerland, Mar 03 2023 *)

Crossrefs

Sequence in context: A067737 A217218 A111494 * A250329 A242515 A156812

Adjacent sequences: A092022 A092023 A092024 * A092026 A092027 A092028

Keyword

nonn,base,more

Author

Farideh Firoozbakht, Feb 19 2004

Extensions

Edited by Charles R Greathouse IV, Apr 29 2010

a(6) from Max Alekseyev, Jan 28 2012

Status

approved