

A101958


Indices of primes in sequence defined by A(0) = 23, A(n) = 10*A(n1) + 13 for n > 0.


1



0, 3, 6, 11, 29, 93, 177, 195, 563, 1800, 3519, 3537, 8232, 35160, 37404, 42329, 70050, 90791
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OFFSET

1,2


COMMENTS

Numbers n such that (220*10^n  13)/9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime.
Numbers corresponding to terms <= 563 are certified primes.
With changed signs, expansion of sinh(atan(x)).
Next term after 3537 is greater than 5000.  Ryan Propper, Jun 16 2005


REFERENCES

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462467.


LINKS



FORMULA



EXAMPLE

24443 is prime, hence 3 is a term.


PROG

(PARI) a=23; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a+13)
(PARI) for(n=0, 2000, if(isprime((220*10^n13)/9), print1(n, ", ")))


CROSSREFS



KEYWORD

nonn,hard,more


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 23 2004


EXTENSIONS

8232 from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007


STATUS

approved



