A271375 Numbers k such that (38*10^k + 637)/9 is prime.

1, 4, 14, 19, 25, 26, 32, 41, 59, 79, 83, 101, 103, 200, 308, 314, 548, 565, 620, 922, 1102, 1960, 2245, 2254, 5393, 5935, 6227, 14350, 25070

Offset

1,2

Comments

For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 2 followed by the digits 93 is prime (see Example section).

a(30) > 2*10^5.

Links

Table of n, a(n) for n=1..29.

Makoto Kamada, Search for 42w93.

Example

4 is in this sequence because (38*10^4+637)/9 = 42293 is prime.
Initial terms and primes associated:
a(1) = 1, 113;
a(2) = 4, 42293;
a(3) = 14, 422222222222293;
a(4) = 19, 42222222222222222293;
a(5) = 25, 42222222222222222222222293, etc.

Mathematica

Select[Range[0, 100000], PrimeQ[(38*10^# + 637)/9] &]

Prog

(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime((38*10^n + 637)/9), print1(n, ", "))); \\ Altug Alkan, Apr 05 2016

Crossrefs

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

Sequence in context: A022383 A336634 A045248 * A070902 A059007 A035401

Adjacent sequences: A271372 A271373 A271374 * A271376 A271377 A271378

Keyword

nonn,more

Author

Robert Price, Apr 05 2016

Status

approved