A242550 Prime numbers that will become composite after removing any group of initial digits.

19, 29, 59, 79, 89, 109, 139, 149, 199, 239, 269, 349, 409, 439, 449, 499, 509, 569, 599, 709, 739, 769, 809, 839, 1009, 1039, 1049, 1069, 1249, 1399, 1549, 1609, 1669, 1699, 1949, 1999, 2039, 2069, 2099, 2309, 2339, 2399, 2539, 2549, 2609, 2699, 2749, 2909

Offset

1,1

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Example

127 is not a term because 7 is prime.
139 is a term because 139 is prime but 39 and 9 are composite.

Prog

(PARI) arecomp(p) = {nbd = #digits(p); for (i=1, nbd-1, if (isprime(q=(p % 10^i)) || (q==1), return(0)); ); return (1); }
isokp(p) = (p>10) && isprime(p) && arecomp(p); \\ Michel Marcus, May 17 2014

Crossrefs

Cf. A242265.

Subsequence of A030433 and A242265.

Sequence in context: A242265 A004618 A030433 * A141311 A090148 A348561

Adjacent sequences: A242547 A242548 A242549 * A242551 A242552 A242553

Keyword

nonn,base

Author

J. Lowell, May 17 2014

Extensions

More terms from Michel Marcus, May 17 2014

Status

approved