login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A242550 Prime numbers that will become composite after removing any group of initial digits. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A242265.

LINKS

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

EXAMPLE

127 doesn't qualify because 7 is prime.

139 qualifies 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.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 16:13 EST 2021. Contains 349557 sequences. (Running on oeis4.)