|
Search: id:A101541
|
|
|
| A101541 |
|
Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) + 81 for n > 0. |
|
+0
1
|
|
| 0, 1, 2, 3, 13, 14, 22, 27, 53, 99, 271, 372, 402, 567, 638, 841, 968, 1254, 1258, 3046, 4837, 6388, 12754, 15141
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
Numbers n such that (630*10^n - 81)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 9 followed by digit 1 is prime.
Numbers corresponding to terms <= 968 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
|
69991 is prime, hence 3 is a term.
|
|
PROGRAM
|
(PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+81)
(PARI) for(n=0, 1500, if(isprime((630*10^n-81)/9), print1(n, ", ")))
|
|
CROSSREFS
|
Cf. A000533, A002275.
a(n) = A103048(n) - 1.
Sequence in context: A056445 A100385 A128460 this_sequence A059670 A038975 A059456
Adjacent sequences: A101538 A101539 A101540 this_sequence A101542 A101543 A101544
|
|
KEYWORD
|
nonn,hard,more
|
|
AUTHOR
|
Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
|
|
EXTENSIONS
|
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
|
|
|
Search completed in 0.002 seconds
|
