|
| |
|
|
A101954
|
|
Indices of primes in sequence defined by A(0) = 27, A(n) = 10*A(n-1) - 53 for n > 0.
|
|
1
|
| |
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Numbers n such that (190*10^n + 53)/9 is prime.
Numbers n such that digit 2 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
Numbers corresponding to terms <= 392 are certified primes.
No further terms up to n=5000. [Harvey P. Dale, Aug 20 2011]
a(7) > 10^5. - Robert Price, Feb 07 2015
|
|
|
REFERENCES
|
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
|
|
|
LINKS
|
Table of n, a(n) for n=1..6.
Makoto Kamada, Factorizations of 211...117.
Index entries for primes involving repunits.
|
|
|
FORMULA
|
a(n) = A102949(n) - 1.
|
|
|
EXAMPLE
|
2111111111111111111111111111111111117 is prime, hence 35 is a term.
|
|
|
MATHEMATICA
|
a = 27; Flatten[Position[Table[a = 10*a - 53, {n, 500}], _?(PrimeQ[#] &)]]
|
|
|
PROG
|
(PARI) a=27; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-53)
(PARI) for(n=0, 1500, if(isprime((190*10^n+53)/9), print1(n, ", ")))
|
|
|
CROSSREFS
|
Cf. A000533, A002275, A102949.
Sequence in context: A219825 A194716 A220047 * A220201 A005937 A341043
Adjacent sequences: A101951 A101952 A101953 * A101955 A101956 A101957
|
|
|
KEYWORD
|
nonn,hard,more
|
|
|
AUTHOR
|
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004
|
|
|
EXTENSIONS
|
a(5)-a(6) derived from A102949 by Robert Price, Feb 07 2015
|
|
|
STATUS
|
approved
|
| |
|
|
