

A101738


Indices of primes in sequence defined by A(0) = 41, A(n) = 10*A(n1) + 81 for n > 0.


1



0, 1, 3, 6, 23, 171, 172, 217, 438, 2562, 2781, 2879, 3714, 4391, 10819, 14591, 25053, 27768, 40167, 180991, 193906
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OFFSET

1,3


COMMENTS

Numbers n such that (450*10^n  81)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 9 followed by digit 1 is prime.
Numbers corresponding to terms <= 438 are certified primes.


REFERENCES

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


LINKS



FORMULA



EXAMPLE

49991 is prime, hence 3 is a term.


MATHEMATICA

Select[Range[0, 1000], PrimeQ[(450*10^#  81)/9] &] (* Robert Price, May 30 2015 *)


PROG

(PARI) a=41; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+81)
(PARI) for(n=0, 1500, if(isprime((450*10^n81)/9), print1(n, ", ")))


CROSSREFS



KEYWORD

nonn,hard,more


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 14 2004


EXTENSIONS

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


STATUS

approved



