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A101730 Indices of primes in sequence defined by A(0) = 43, A(n) = 10*A(n-1) + 33 for n > 0. 1
0, 1, 2, 3, 5, 6, 7, 11, 22, 58, 74, 143, 203, 267, 759, 1215, 1429, 1505, 1508, 2803, 2923, 3200, 3304, 5752, 9267, 11278, 19676, 23413, 28626, 31361, 42298, 49118, 63746, 81766 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Numbers n such that (420*10^n - 33)/9 is prime.

Numbers n such that digit 4 followed by n >= 0 occurrences of digit 6 followed by digit 3 is prime.

Numbers corresponding to terms <= 759 are certified primes.

a(35) > 10^5. - Robert Price, Mar 30 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..34.

Makoto Kamada, Prime numbers of the form 466...663.

Index entries for primes involving repunits.

FORMULA

a(n) = A099005(n) - 1.

EXAMPLE

463 is prime, hence 1 is a term.

MATHEMATICA

Select[Range[0, 100], PrimeQ[(420*10^# - 33)/9] &]

PROG

(PARI) a=43; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+33)

(PARI) for(n=0, 1500, if(isprime((420*10^n-33)/9), print1(n, ", ")))

CROSSREFS

Cf. A000533, A002275, A099005.

Sequence in context: A098959 A071251 A077571 * A276692 A169829 A189208

Adjacent sequences:  A101727 A101728 A101729 * A101731 A101732 A101733

KEYWORD

nonn,hard,more

AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(28)-a(34) derived from A099005 by Robert Price, Mar 30 2015

STATUS

approved

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Last modified June 25 12:01 EDT 2019. Contains 324352 sequences. (Running on oeis4.)