A215641 - OEIS

A215641

Smallest prime whose decimal expansion consists of the concatenation of a 1-digit prime, a 2-digit prime, a 3-digit prime, ..., and an n-digit prime.

%I #30 May 06 2022 13:13:51

%S 2,211,211151,2111011129,211101100910009,211101100910007100049,

%T 2111011009100071000031000453,211101100910007100003100000310000721,

%U 211101100910007100003100000310000019100000543,2111011009100071000031000003100000191000000071000000531

%N Smallest prime whose decimal expansion consists of the concatenation of a 1-digit prime, a 2-digit prime, a 3-digit prime, ..., and an n-digit prime.

%C It is a plausible conjecture that a(n) always exists.

%C a(n) has A000217(n) = n*(n+1)/2 digits.

%e a(4) = 2111011129, the smallest prime formed from a single-digit, a double-digit, a triple-digit, and a quadruple-digit prime, i.e., 2, 11, 101, 1129.

%Y Cf. A000040, A000217, A003617.

%Y Subsequence of A195302.

%Y Cf. A338968 (similar, with largest prime).

%K nonn,base

%O 1,1

%A _Jonathan Vos Post_, Aug 18 2012

%E Edited by _N. J. A. Sloane_, Aug 18 2012