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A275978 Numbers n such that (101*10^n + 1)/3 is prime. 0
1, 4, 6, 12, 34, 54, 60, 61, 73, 148, 349, 552, 649, 967, 1044, 2521, 4501, 5721, 6133, 9052, 9880, 16126, 16215, 19146, 61770 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that the digits 33 followed by n-1 occurrences of the digit 6 followed by the digit 7 is prime (see Example section).

a(26) > 10^5.

LINKS

Table of n, a(n) for n=1..25.

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

Makoto Kamada, Search for 336w7.

EXAMPLE

4 is in this sequence because (101*10^4 + 1)/3 = 336667 is prime.

Initial terms and primes associated:

a(1) = 1, 337;

a(2) = 4, 336667;

a(3) = 6, 33666667;

a(4) = 12, 33666666666667;

a(5) = 34, 336666666666666666666666666666666667, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(101*10^# + 1)/3] &]

PROG

(PARI) isok(n) = isprime((101*10^n + 1)/3); \\ Michel Marcus, Aug 16 2016

CROSSREFS

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

Sequence in context: A027070 A087785 A081198 * A242211 A073167 A060202

Adjacent sequences:  A275975 A275976 A275977 * A275979 A275980 A275981

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 15 2016

STATUS

approved

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Last modified August 8 05:25 EDT 2020. Contains 336290 sequences. (Running on oeis4.)