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A101824
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Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) - 63 for n > 0.
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0
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0, 1, 4, 7, 23, 28, 83, 109, 128, 175, 592, 1136, 2674, 4991
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Numbers n such that 30*10^n + 7 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 0 followed by digit 7 is prime.
Numbers corresponding to terms <= 592 are certified primes.
a(n) = A100501(n-1) - 1.
No further terms <= 3336. - Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Dec 26 2004
Certified primality of term 1136 using Primo. - Ryan Propper (rpropper(AT)stanford.edu), Jun 18 2005
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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
| 307 is prime, hence 1 is a term.
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PROG
| (PARI) a=37; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-63)
(PARI) for(n=0, 1500, if(isprime(30*10^n+7), print1(n, ", ")))
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CROSSREFS
| Cf. A000533, A002275, A100501.
a(n) = A100501(n) - 1.
Sequence in context: A073114 A083830 A086968 * A027946 A203230 A143608
Adjacent sequences: A101821 A101822 A101823 * A101825 A101826 A101827
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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
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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