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A115073 Numbers n such that 10^(2n+1)-7*10^n-1 is prime. 46
1, 8, 9, 352, 530, 697, 1315, 1918, 2874, 5876, 6768, 62938, 134739 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
REFERENCES
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
LINKS
Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
FORMULA
a(n) = (A077778(n)-1)/2.
MATHEMATICA
Do[If[PrimeQ[10^(2n + 1) - 7*10^n - 1], Print[n]], {n, 3000}]
PROG
(PARI) for(n=0, 1e4, if(ispseudoprime(t=10^(2*n+1)-7*10^n-1), print1(t", "))) \\ Charles R Greathouse IV, Jul 15 2011
CROSSREFS
Sequence in context: A294468 A041605 A239524 * A298020 A042393 A264777
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Mar 03 2006
EXTENSIONS
Edited by Ray Chandler, Dec 28 2010
Added two more terms from PWP table, by Patrick De Geest, Nov 05 2014
STATUS
approved

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Last modified February 27 08:19 EST 2024. Contains 370367 sequences. (Running on oeis4.)