

A240768


Lefttruncatable primes p with property that prepending any single decimal digit to p does not produce a prime.


1



2, 5, 773, 3373, 3947, 4643, 5113, 6397, 6967, 7937, 15647, 16823, 24373, 33547, 34337, 37643, 56983, 57853, 59743, 62383, 63347, 63617, 69337, 72467, 72617, 75653, 76367, 87643, 92683, 97883, 98317, 121997, 124337, 163853, 213613, 236653, 242467, 242797
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..38.
Chris Caldwell, The Prime Glossary, Lefttruncatable prime
Eric Weisstein's World of Mathematics, Truncatable Prime
Index entries for sequences related to truncatable primes


FORMULA

A024785 INTERSECT A155762.


EXAMPLE

3373 belongs to this sequence because 3373, 373, 73 and 3 are all prime; k*10^4 + 3373, for k = 1 to 9, are all composite.


PROG

(PARI) for(n=2, 242797, v=n; while(isprime(n), c=n; n=lift(Mod(c, 10^(#Str(c)1))); if(!(#Str(c)#Str(n)==1), break)); if(n==0, s=#Str(v); t=0; for(k=1, 9, if(isprime(k*10^s+v), break, t++)); if(t==9, print1(v, ", "))); n=v);


CROSSREFS

Subsequence of A024785 and of A155762.
Sequence in context: A065588 A208277 A131748 * A212590 A208212 A176117
Adjacent sequences: A240765 A240766 A240767 * A240769 A240770 A240771


KEYWORD

nonn,base,fini


AUTHOR

Arkadiusz Wesolowski, Apr 12 2014


STATUS

approved



