A102931 -id:A102931 - cp's OEIS frontend

A102011 Indices of primes in sequence defined by A(0) = 19, A(n) = 10*A(n-1) - 61 for n > 0.

0, 2, 5, 50, 56, 62, 149, 392, 419, 546, 42023, 43062, 101612, 107384

Offset: 1

Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004

Numbers n such that (110*10^n + 61)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 2 followed by digit 9 is prime.
Numbers corresponding to terms <= 546 are certified primes.
a(13) > 10^5. - Robert Price, Jan 17 2015
a(15) > 2*10^5. - Tyler Busby, Feb 01 2023

			1222229 is prime, hence 5 is a term.

Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

Makoto Kamada, Prime numbers of the form 122...229.
Index entries for primes involving repunits.

Cf. A000533, A002275, A102931.

a=19;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-61)

for(n=0,1500,if(isprime((110*10^n+61)/9),print1(n,",")))

a(n) = A102931(n) - 1.

a(11)-a(12) derived from A102931 by Robert Price, Jan 17 2015

a(13)-a(14) from Tyler Busby, Jan 31 2023

A102632 Smallest k such that at least one of 2^k+/-prime(n) is prime.

Original entry on oeis.org

0, 1, 1, 2, 1, 2, 1, 2, 3, 1, 4, 2, 1, 2, 5, 3, 1, 6, 2, 1, 4, 2, 7, 3, 2, 1, 2, 1, 2, 7, 2, 3, 1, 9, 1, 4, 4, 2, 5, 3, 1, 4, 1, 2, 1, 6, 4, 2, 1, 2, 3, 1, 4, 5, 9, 3, 1, 9, 2, 1, 6, 7, 2, 1, 2, 5, 4, 4, 1, 2, 16, 3, 4, 4, 2, 10, 3, 2, 3, 9, 1, 8, 1, 4, 2, 7, 3, 2, 1, 2, 5, 3, 2, 3, 2, 7, 5, 1, 6, 4, 4, 9, 3, 1

Offset: 1

Lei Zhou, Jan 20 2005

nonn

			For prime(2)=3, 2^1+3 = 5 is prime
For prime(18)=61, 2^6-61 = 3 is prime

Lei Zhou, Between 2^n and primes.

Cf. A102930, A102931, A094076, first occurrence in A103032.

f[n_] := Block[{k = 0, p = Prime[n]}, While[ Not[(2^k - p > 1 && PrimeQ[2^k - p]) || PrimeQ[2^k + p]], k++ ]; k]; Table[ f[n], {n, 104}] (* Robert G. Wilson v, Jan 22 2005 *)

More terms from Robert G. Wilson v, Jan 21 2005

cp's OEIS Frontend

A102011 Indices of primes in sequence defined by A(0) = 19, A(n) = 10*A(n-1) - 61 for n > 0.

Views

Author

Keywords

Comments

Examples

References

Links

Crossrefs

Programs

PARI