

A050987


Number of ndigit lefttruncatable primes.


18



4, 11, 39, 99, 192, 326, 429, 521, 545, 517, 448, 354, 276, 212, 117, 72, 42, 24, 13, 6, 5, 4, 3, 1, 0
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OFFSET

1,1


COMMENTS

The sequence is well defined for any positive integer, with a(n) = 0 for n >= 25. But it makes sense to consider it to be full & finite.  M. F. Hasler, Nov 07 2018


LINKS

Table of n, a(n) for n=1..25.
I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265267, 1977.
P. De Geest, The list of 4260 lefttruncatable primes
Eric Weisstein's World of Mathematics, Truncatable Prime.
Index entries for sequences related to numbers of primes in various ranges
Index entries for sequences related to truncatable primes


PROG

(PARI) A050987=vector(25, n, #p=concat(apply(p>select(isprime, vector(9, i, i*10^(n1)+p)), if(n>1, p)))) \\ M. F. Hasler, Nov 07 2018


CROSSREFS

Cf. A033664, A024785, A032437, A020994, A024770, A052023, A052024, A052025, A050986.
Sequence in context: A149257 A255706 A203161 * A137191 A106269 A126758
Adjacent sequences: A050984 A050985 A050986 * A050988 A050989 A050990


KEYWORD

base,nonn,easy,fini,full


AUTHOR

Eric W. Weisstein


EXTENSIONS

Edited by Ray Chandler, Mar 13 2007
a(25) = 0 added by M. F. Hasler, Nov 07 2018


STATUS

approved



