login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A101520 Indices of primes in sequence defined by A(0) = 67, A(n) = 10*A(n-1) - 53 for n > 0. 1
0, 1, 31, 42, 972, 1194, 4470, 5683, 7987, 46884 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers n such that (550*10^n + 53)/9 is prime.

Numbers n such that digit 6 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.

Numbers corresponding to terms <= 972 are certified primes.

a(11) > 10^5. - Robert Price, Sep 07 2015

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..10.

Makoto Kamada, Prime numbers of the form 611...117.

Index entries for primes involving repunits.

FORMULA

a(n) = A103028(n) - 1.

EXAMPLE

67 is prime, hence 0 is a term.

MATHEMATICA

Select[Range[0, 10000], PrimeQ[(550*10^# + 53)/9] &] (* Robert Price, Sep 07 2015 *)

PROG

(PARI) a=67; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-53)

(PARI) for(n=0, 1500, if(isprime((550*10^n+53)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A103028.

Sequence in context: A040180 A158754 A140458 * A225862 A089713 A281246

Adjacent sequences:  A101517 A101518 A101519 * A101521 A101522 A101523

KEYWORD

nonn,hard,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

a(10) from Erik Branger May 01 2013 by Ray Chandler, Apr 30 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 17 12:33 EDT 2019. Contains 328112 sequences. (Running on oeis4.)