|
|
A101009
|
|
Indices of primes in sequence defined by A(0) = 91, A(n) = 10*A(n-1) + 41 for n > 0.
|
|
1
|
|
|
2, 5, 17, 29, 87, 92, 153, 176, 227, 572, 896, 980, 1415, 1449, 3365, 4931, 5193, 13478, 18608, 23345, 51423, 74675, 80570
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
Numbers n such that (860*10^n - 41)/9 is prime.
Numbers n such that digit 9 followed by n >= 0 occurrences of digit 5 followed by digit 1 is prime.
Numbers corresponding to terms <= 980 are certified primes.
|
|
REFERENCES
|
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
9551 is prime, hence 2 is a term.
|
|
MATHEMATICA
|
Flatten[Position[NestList[10#+41&, 91, 5200], _?PrimeQ]-1] (* Harvey P. Dale, Jun 28 2012 *)
Select[Range[0, 100000], PrimeQ[(860*10^# - 41)/9] &] (* Robert Price, Nov 10 2015 *)
|
|
PROG
|
(PARI) a=91; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+41)
(PARI) for(n=0, 1500, if(isprime((860*10^n-41)/9), print1(n, ", ")))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,hard,more,less
|
|
AUTHOR
|
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004
|
|
EXTENSIONS
|
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
|
|
STATUS
|
approved
|
|
|
|