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A056248
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Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) + 61 for n > 0.
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0
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OFFSET
| 1,2
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COMMENTS
| Numbers n such that (160*10^n - 61)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 7 followed by digit 1 is prime.
Numbers corresponding to terms <= 365 are certified primes.
a(n) = A082701(n-2) - 2 for n > 1.
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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 177...771.
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EXAMPLE
| 1777771 is prime, hence 5 is a term.
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PROG
| (PARI) a=11; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+61)
(PARI) for(n=0, 1500, if(isprime((160*10^n-61)/9), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275, A082701.
Sequence in context: A196160 A136088 A141890 * A126575 A139889 A134327
Adjacent sequences: A056245 A056246 A056247 * A056249 A056250 A056251
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KEYWORD
| nonn,hard,more
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 18 2000
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EXTENSIONS
| Additional comments from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
Edited by N. J. A. Sloane (njas(AT)research.att.com), Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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