A059017 - OEIS

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A059017

Smallest n-digit prime whose square is a concatenation of two n-digit primes (no leading zeros allowed), 0 if no such prime.

5, 73, 337, 5449, 32569, 316259, 3165713, 31630007, 316229827, 3162291731, 31622777629, 316227771019, 3162277660313, 31622776613849, 316227766047293, 3162277660170061, 31622776601693377, 316227766016857441

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..18.

EXAMPLE

E.g., 5449^2 = 29691601 = (2969)(1601).

PROG

(PARI) { a(n) = local(t, m, s); t = 10^(n-1); while(1, t=nextprime(t+1); m = nextprime(sqrtint(t*10^n)+1); s=m^2; if( s\10^n!=t, next); if( (s%10^n) > 10^(n-1) && ispseudoprime(s%10^n), return(m); ); ) } \\ Max Alekseyev, Apr 23 2010

CROSSREFS

Sequence in context: A070526 A070530 A248046 * A099667 A108444 A155662

Adjacent sequences: A059014 A059015 A059016 * A059018 A059019 A059020

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jan 15 2001

EXTENSIONS

More terms from Max Alekseyev, Apr 23 2010

STATUS

approved