A290407 Primes obtained from other primes by prefixing an 8.

83, 811, 823, 829, 853, 859, 883, 8101, 8167, 8179, 8191, 8233, 8263, 8269, 8293, 8311, 8317, 8353, 8389, 8419, 8431, 8443, 8461, 8467, 8521, 8563, 8599, 8641, 8647, 8677, 8719, 8761, 8821, 8839, 8863, 8887, 8929, 8941, 8971, 81013, 81019, 81031, 81049, 81097

Offset: 1

Author

K. D. Bajpai, Jul 30 2017

Keywords

• nonn
• base

Comments

Except a(1), all the terms in this sequence are congruent to 1 mod 3.

Examples

			823 is in the sequence because it is a prime obtained by prefixing an 8 to the prime 23.
8317 is in the sequence because it is a prime obtained by prefixing an 8 to the prime 317.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A045714.

Cf. A165555, A167187, A289866, A289867.

Programs

Magma

[k : p in PrimesUpTo (5000) | IsPrime (k) where k is Seqint (Intseq (p) cat Intseq (8))];

Maple

A290407:= n-> (parse(cat(8, ithprime(n)))): select(isprime, [seq((A290407 (n), n=1..1000))]);

Mathematica

Select[k = 8; Table[FromDigits[Join[IntegerDigits[k], IntegerDigits[Prime[n]]]], {n, 500}], PrimeQ]

PARI

forprime(p = 2,5000, k=eval(concat(8,Str(p))); if(isprime(k), print1(k,", ")));