1,1

This is to Champernowne's constant 0.12345678910111213... (Sloane's A033307) as A073062 is to A033308 Decimal expansion of Copeland-Erdos constant: concatenate primes. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2008]

Eric W. Weisstein, Champernowne Constant. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2008]

Eric W. Weisstein, Copeland-Erdos Constant. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2008]

Take 1234567891011121314151617....; a(4)=4567 because the first 4-digit prime in the sequence is 4567.

1213 is < 4567 but occurs later in the string.

a(5) = 67891 is the first occurrence of a five-digit substring that is a prime, 12345(67891)011121314...

a(1) = 2 = prime(1). a(2) = 23 = prime(9). a(3) = 571 = prime(105). a(4) = 2357 = prime(350). a(5) = 11131 = prime(1349). [From Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2008]

p200=Flatten[IntegerDigits[Range[200]]]; Do[pn=Partition[p200, n, 1]; ln=Length[pn]; tab=Table[Sum[10^(n-k)*pn[[i, k]], {k, n}], {i, ln}]; Print[{n, Select[tab, PrimeQ][[1]]}], {n, 20}]

Contribution from M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Aug 23 2008: (Start)

(PARI) {s=Vec(Str(c=1)); for(d=1, 30, for(j=1, 9e9,

#s<d+j && s=concat( s, Vec( Str( c++ ))); s[j]=="0" && next;

isprime( p=eval( concat( vecextract( s, Str(j, "..", j+d-1) )))) || next;

print(d, " ", p); next(2)))} /* replace "isprime" by 2==bigomega to get the semiprime analogue */ (End)

Cf. A003617 [From M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Aug 23 2008]

Cf. A000040, A033307, A033308, A073062. [From Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2008]

Sequence in context: A131176 A141405 A068876 this_sequence A141888 A034523 A143912

Adjacent sequences: A073172 A073173 A073174 this_sequence A073176 A073177 A073178

base,nonn

Zak Seidov (zakseidov(AT)yahoo.com), Aug 22 2002

Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 19 2008 at the suggestion of R. J. Mathar