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A109991 Numbers k such that the string 88k is prime. 1
1, 3, 7, 19, 21, 31, 37, 39, 49, 61, 63, 67, 87, 93, 117, 129, 169, 177, 211, 223, 237, 241, 259, 261, 289, 301, 321, 327, 337, 339, 379, 397, 411, 423, 427, 463, 469, 471, 493, 499, 513, 523, 547, 589, 591, 607, 609, 643, 651, 657, 661, 663, 667, 681, 721, 729 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
EXAMPLE
If k=1 then 88k = 881, which is prime.
If k=61 then 88k = 8861, which is prime.
MAPLE
a:= proc(n) local k; for k from 1 +`if`(n=1, 0, a(n-1))
while not isprime(parse(""||88||k)) do od; a(n):=k
end:
seq(a(n), n=1..100); # Alois P. Heinz, Jul 30 2014
MATHEMATICA
Select[Range[900], PrimeQ[88 10^IntegerLength[#] + #] &] (* Vincenzo Librandi, Jul 30 2014 *)
PROG
(Magma) [n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [8, 8])) ]; // Vincenzo Librandi, Jul 30 2014
CROSSREFS
Sequence in context: A032675 A089749 A032667 * A248219 A322963 A018432
KEYWORD
nonn,base
AUTHOR
Parthasarathy Nambi, Sep 01 2005
EXTENSIONS
More terms from Vincenzo Librandi, Mar 27 2010
STATUS
approved

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Last modified May 19 02:13 EDT 2024. Contains 372666 sequences. (Running on oeis4.)