A093162 - OEIS

A093162

Primes of the form 20*R_k + 3, where R_k is the repunit (A002275) of length k.

3, 23, 223, 22222223, 22222222223, 222222222222222222222222222222222223

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OFFSET

1,1

COMMENTS

The next term (a(7)) has 95 digits. - Harvey P. Dale, Dec 26 2022

LINKS

FORMULA

a(n) = (20*10^A056656(n) + 7)/9 = (2*10^A096506(n) + 7)/9.

MATHEMATICA

Select[Table[FromDigits[PadLeft[{3}, n, 2]], {n, 40}], PrimeQ] (* Harvey P. Dale, Dec 26 2022 *)

CROSSREFS

Cf. A002275, A056656 (corresponding k, and count of digits 2 in a(n)), A096506.

KEYWORD

nonn

AUTHOR

EXTENSIONS

Edited by Ray Chandler, Feb 27 2012

STATUS

approved