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A101077
Indices of primes in sequence defined by A(0) = 83, A(n) = 10*A(n-1) + 43 for n > 0.
1
0, 6, 35, 98, 324, 1226, 9260, 9413, 11114, 25148, 43211
OFFSET
1,2
COMMENTS
Numbers n such that (790*10^n - 43)/9 is a prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.
Numbers corresponding to terms <= 324 are certified primes.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
FORMULA
a(n) = A103090(n) - 1.
EXAMPLE
87777773 is prime, hence 6 is a term.
MATHEMATICA
#-1&/@(Flatten[Position[NestList[10#+43&, 83, 10000], _?PrimeQ]]) (* Harvey P. Dale, May 20 2011 *)
PROG
(PARI) a=83; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+43)
(PARI) for(n=0, 1500, if(isprime((790*10^n-43)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(9)-a(11) from Kamada data by Ray Chandler, Apr 29 2015
STATUS
approved