|
Search: id:A101075
|
|
|
| A101075 |
|
Indices of primes in sequence defined by A(0) = 89, A(n) = 10*A(n-1) - 21 for n > 0. |
|
+0
1
|
|
| 0, 2, 16, 18, 32, 38, 168, 452, 610, 882, 1472, 6510, 9646
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
Numbers n such that (780*10^n + 21)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 6 followed by digit 9 is prime.
Numbers corresponding to terms <= 882 are certified primes.
|
|
REFERENCES
|
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
|
|
LINKS
|
Makoto Kamada, Factorizations of near-repdigit numbers.
|
|
EXAMPLE
|
8669 is prime, hence 2 is a term.
|
|
PROGRAM
|
(PARI) a=89; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-21)
(PARI) for(n=0, 1500, if(isprime((780*10^n+21)/9), print1(n, ", ")))
|
|
CROSSREFS
|
Cf. A000533, A002275.
a(n) = A103088(n) - 1.
Sequence in context: A004831 A058242 A114974 this_sequence A022370 A161802 A050850
Adjacent sequences: A101072 A101073 A101074 this_sequence A101076 A101077 A101078
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) 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
|
|
|
Search completed in 0.002 seconds
|
