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A056255 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 43 for n > 0. 1
1, 13, 53, 67, 83, 85, 155, 2765, 3379, 3875, 5207, 10745, 15767, 31315, 40957, 45803, 46565, 51007, 80161 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers n such that (340*10^n - 43)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.
Numbers corresponding to terms <= 5207 are certified primes.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
Patrick De Geest, PDP Reference Table - 373.
FORMULA
a(n) = A082708(n) - 2.
EXAMPLE
373 is prime, hence 1 is a term.
MATHEMATICA
Select[Range[0, 2000], PrimeQ[(340 10^# - 43) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
PROG
(PARI) a=33; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+43)
(PARI) for(n=0, 1500, if(isprime((340*10^n-43)/9), print1(n, ", ")))
CROSSREFS
Sequence in context: A317467 A076163 A207977 * A141885 A262447 A165352
KEYWORD
nonn,hard,more
AUTHOR
Robert G. Wilson v, Aug 18 2000
EXTENSIONS
Additional comments from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Two more terms from PDP table and a link added, and comments section updated, by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 05 2014
STATUS
approved

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Last modified March 28 07:30 EDT 2024. Contains 371235 sequences. (Running on oeis4.)