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A101828
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Indices of primes in sequence defined by A(0) = 31, A(n) = 10*A(n-1) + 11 for n > 0.
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0
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that (290*10^n - 11)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 2 followed by digit 1 is prime.
Numbers corresponding to terms <= 962 are certified primes.
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REFERENCES
| Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
| Makoto Kamada, Factorizations of near-repdigit numbers.
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EXAMPLE
| 3221 is prime, hence 2 is a term.
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PROG
| (PARI) a=31; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+11)
(PARI) for(n=0, 1500, if(isprime((290*10^n-11)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275.
a(n) = A102966(n) - 1.
Sequence in context: A107989 A069504 A158997 * A071293 A109623 A127532
Adjacent sequences: A101825 A101826 A101827 * A101829 A101830 A101831
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KEYWORD
| nonn,hard,more
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
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EXTENSIONS
| 2699 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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