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A271146 Numbers k such that (16*10^k - 19)/3 is prime. 0
1, 4, 5, 6, 10, 13, 20, 22, 24, 35, 41, 42, 46, 155, 222, 336, 432, 538, 577, 637, 679, 750, 758, 785, 2262, 5436, 6806, 7962, 9757, 16016, 24588, 47918, 59062, 74092, 81896, 85495, 102299, 185978, 190420 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 5 followed by k-2 occurrences of the digit 3 followed by the digits 27 is prime (see Example section).

a(40) > 2*10^5.

LINKS

Table of n, a(n) for n=1..39.

Makoto Kamada, Search for 53w27.

EXAMPLE

4 is in this sequence because (16*10^4 - 19)/3 = 53327 is prime.

Initial terms and primes associated:

a(1) = 1, 47;

a(2) = 4, 53327;

a(3) = 5, 533327;

a(4) = 6, 5333327;

a(5) = 10, 53333333327;

a(6) = 13, 53333333333327, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(16*10^# - 19)/3] &]

PROG

(PARI) lista(nn) = {for(n=1, nn, if(ispseudoprime((16*10^n - 19)/3), print1(n, ", "))); } \\ Altug Alkan, Mar 31 2016

CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A270974.

Sequence in context: A186808 A114439 A310570 * A347806 A079257 A001609

Adjacent sequences:  A271143 A271144 A271145 * A271147 A271148 A271149

KEYWORD

nonn,more

AUTHOR

Robert Price, Mar 31 2016

EXTENSIONS

a(37)-a(39) from Robert Price, Feb 23 2019

STATUS

approved

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Last modified October 17 21:17 EDT 2021. Contains 348065 sequences. (Running on oeis4.)