A275285 Numbers k such that 33*10^k + 7 is prime.

1, 2, 5, 6, 30, 58, 66, 127, 138, 179, 287, 520, 767, 954, 966, 1254, 1313, 1976, 2266, 2496, 3137, 4058, 4411, 7009, 11736, 12155, 21328, 31124, 31589, 38581, 42683, 54634, 56634, 85297

Offset

1,2

Comments

For k > 0, numbers k such that the digits 33 followed by k-1 occurrences of the digit 0 followed by the digit 7 is prime (see Example section).

a(35) > 10^5.

Links

Table of n, a(n) for n=1..34.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 330w7.

Example

5 is in this sequence because 33*10^5 + 7 = 3300007 is prime.
Initial terms and associated primes:
a(1) = 1, 337;
a(2) = 2, 3307;
a(3) = 5, 3300007;
a(4) = 6, 33000007;
a(5) = 30, 33000000000000000000000000000007, etc.

Mathematica

Select[Range[0, 100000], PrimeQ[33*10^# + 7] &]

Prog

(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(33*10^n+7), print1(n, ", "))); \\ Altug Alkan, Jul 21 2016

Crossrefs

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A056441 A365085 A164805 * A360085 A152918 A276845

Adjacent sequences: A275282 A275283 A275284 * A275286 A275287 A275288

Keyword

nonn,more

Author

Robert Price, Jul 21 2016

Status

approved