

A089987


Primes in the concatenation of consecutive numbers beginning with 2.


6




OFFSET

1,1


COMMENTS

Sum of reciprocals = 0.5434783035011462065880780409..
23, 4567 and 89 are prime numbers, thus a(3) = A262571(9) = 23456789 is a prime obtained by concatenating 3 primes that are themselves the concatenation of consecutive integers.  XU Pingya, Apr 16 2017


LINKS

Table of n, a(n) for n=1..4.


PROG

(PARI) concatprime(n, p) = { sr=0; y=""; for(x=p, n, y=concat(Str(y), Str(x)); z=eval(y); if(ispseudoprime(z), print1(z", "); sr+=1./z; ); ); print(); print(sr) }


CROSSREFS

Primes in A262571.
See A262300 for more information.
Sequence in context: A114256 A110714 A067837 * A162605 A118812 A228241
Adjacent sequences: A089984 A089985 A089986 * A089988 A089989 A089990


KEYWORD

nonn,base,more


AUTHOR

Cino Hilliard, Jan 14 2004


EXTENSIONS

Offset corrected by Michel Marcus, Apr 21 2017


STATUS

approved



