A072804 n-th prime prime(n) written in base (prime(n) (mod 4)).

10, 10, 11111, 21, 102, 1111111111111, 11111111111111111, 201, 212, 11111111111111111111111111111, 1011, 1111111111111111111111111111111111111, 11111111111111111111111111111111111111111, 1121, 1202, 11111111111111111111111111111111111111111111111111111, 2012

Offset: 1

Author

Labos Elemer, Jul 12 2002

Keywords

• base
• nonn

Examples

			4k+1 primes are written in base 1, while 4k+3 primes are in base 3.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..168

Crossrefs

Cf. A008713, A072803, A072805, A072806, A072807.

Programs

Mathematica

Table[FromDigits@ If[#2 == 1, ConstantArray[1, #1], IntegerDigits[#1, #2]] & @@ {#, Mod[#, 4]} &@ Prime@ w, {w, 17}] (* Michael De Vlieger, Sep 04 2019 *)

PARI

a(n) = {my(p=prime(n)); if ((p % 4) != 1, fromdigits(digits(p, p % 4), 10), fromdigits(vector(p, k, 1), 10));} \\ Michel Marcus, Sep 04 2019