|
| |
|
|
A101525
|
|
Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) + 21 for n > 0.
|
|
0
| |
|
|
0, 1, 3, 6, 17, 18, 22, 23, 33, 40, 55, 63, 83, 148, 271, 754, 1271, 2397, 2685, 4799, 5197, 6216, 8736
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,3
|
|
|
COMMENTS
| Numbers n such that (570*10^n - 21)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 3 followed by digit 1 is prime.
Numbers corresponding to terms <= 754 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
| 631 is prime, hence 1 is a term.
|
|
|
PROG
| (PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+21)
(PARI) for(n=0, 1500, if(isprime((570*10^n-21)/9), print1(n, ", ")))
|
|
|
CROSSREFS
| Cf. A000533, A002275.
a(n) = A103032(n) - 1.
Sequence in context: A195996 A036050 A173877 * A139476 A063618 A024823
Adjacent sequences: A101522 A101523 A101524 * A101526 A101527 A101528
|
|
|
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
|
| |
|
|
