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A056256 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 53 for n > 0. 1
1, 11, 29, 59, 115, 289, 631, 1063, 1493, 5431, 7361 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that (350*10^n - 53)/9 is prime.

Numbers n such that digit 3 followed by n >= 0 occurrences of digit 8 followed by digit 3 is prime.

Numbers corresponding to terms <= 1493 are certified primes. For larger numbers see P. De Geest, PDP Reference Table.

REFERENCES

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

LINKS

Table of n, a(n) for n=1..11.

Patrick De Geest, PDP Reference Table - 383.

Makoto Kamada, Prime numbers of the form 388...883.

Index entries for primes involving repunits.

FORMULA

a(n) = A082709(n) - 2.

EXAMPLE

383 is prime, hence 1 is a term.

MATHEMATICA

Select[Range[0, 2000], PrimeQ[(350 10^# - 53) / 9] &] (* Vincenzo Librandi, Nov 03 20124 *)

PROG

(PARI) a=33; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+53)

(PARI) for(n=0, 1500, if(isprime((350*10^n-53)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A082709.

Sequence in context: A193880 A138248 A054692 * A171667 A043139 A043919

Adjacent sequences:  A056253 A056254 A056255 * A056257 A056258 A056259

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, Jun 15 2007

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

Comments section and a link updated by Patrick De Geest, Nov 02 2014

Edited by Ray Chandler, Nov 05 2014

STATUS

approved

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Last modified November 16 15:49 EST 2018. Contains 317274 sequences. (Running on oeis4.)