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 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 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

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Last modified March 3 17:50 EST 2024. Contains 370512 sequences. (Running on oeis4.)