|
Search: id:A101965
|
|
|
| A101965 |
|
Indices of primes in sequence defined by A(0) = 29, A(n) = 10*A(n-1) - 21 for n > 0. |
|
+0
1
|
|
| 0, 1, 3, 6, 13, 19, 38, 101, 155, 456, 1189, 2307, 5869, 8313, 9702
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
Numbers n such that (240*10^n + 21)/9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 6 followed by digit 9 is prime.
Numbers corresponding to terms <= 456 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
|
26669 is prime, hence 3 is a term.
|
|
PROGRAM
|
(PARI) a=29; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-21)
(PARI) for(n=0, 1500, if(isprime((240*10^n+21)/9), print1(n, ", ")))
|
|
CROSSREFS
|
Cf. A000533, A002275.
a(n) = A102957(n) - 1.
Sequence in context: A080546 A080554 A064349 this_sequence A064290 A064621 A047172
Adjacent sequences: A101962 A101963 A101964 this_sequence A101966 A101967 A101968
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004
|
|
EXTENSIONS
|
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
|
|
|
Search completed in 0.002 seconds
|
