A101077 Indices of primes in sequence defined by A(0) = 83, A(n) = 10*A(n-1) + 43 for n > 0.

0, 6, 35, 98, 324, 1226, 9260, 9413, 11114, 25148, 43211

Offset

1,2

Comments

Numbers n such that (790*10^n - 43)/9 is a prime.

Numbers n such that digit 8 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.

Numbers corresponding to terms <= 324 are certified primes.

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..11.

Makoto Kamada, Prime numbers of the form 877...773.

Index entries for primes involving repunits.

Formula

a(n) = A103090(n) - 1.

Example

87777773 is prime, hence 6 is a term.

Mathematica

#-1&/@(Flatten[Position[NestList[10#+43&, 83, 10000], _?PrimeQ]]) (* Harvey P. Dale, May 20 2011 *)

Prog

(PARI) a=83; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+43)
(PARI) for(n=0, 1500, if(isprime((790*10^n-43)/9), print1(n, ", ")))

Crossrefs

Cf. A000533, A002275, A103090.

Sequence in context: A369351 A370091 A033578 * A094952 A024526 A213504

Adjacent sequences: A101074 A101075 A101076 * A101078 A101079 A101080

Keyword

nonn,hard,more

Author

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

a(9)-a(11) from Kamada data by Ray Chandler, Apr 29 2015

Status

approved