

A101531


Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n1) + 41 for n > 0.


1



0, 2, 3, 9, 21, 39, 53, 80, 83, 105, 192, 596, 680, 1362, 1875, 4023, 14162, 18732, 20841, 23727, 26418, 31449, 44693, 64766
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OFFSET

1,2


COMMENTS

Numbers n such that (590*10^n  41)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 5 followed by digit 1 is prime.
Numbers corresponding to terms <= 680 are certified primes.


REFERENCES

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462467.


LINKS

Table of n, a(n) for n=1..24.
Makoto Kamada, Prime numbers of the form 655...551.
Index entries for primes involving repunits.


FORMULA

a(n) = A103038(n+1)  1.


EXAMPLE

65551 is prime, hence 3 is a term.


MATHEMATICA

Select[Range[0, 100000], PrimeQ[(590*10^#  41)/9] &] (* Robert Price, Sep 11 2015 *)


PROG

(PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+41)
(PARI) for(n=0, 1500, if(isprime((590*10^n41)/9), print1(n, ", ")))


CROSSREFS

Cf. A000533, A002275, A103038.
Sequence in context: A001004 A015951 A244666 * A099607 A077550 A301809
Adjacent sequences: A101528 A101529 A101530 * A101532 A101533 A101534


KEYWORD

nonn,hard,more,changed


AUTHOR

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwthaachen.de), Dec 06 2004


EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(17)a(23) from Kamada data by Ray Chandler, Apr 30 2015
a(24) from Robert Price, Sep 11 2015


STATUS

approved



