A085821 -id:A085821 - cp's OEIS frontend

A085820 Possible two-digit endings of primes (with leading zeros).

1, 3, 7, 9, 11, 13, 17, 19, 21, 23, 27, 29, 31, 33, 37, 39, 41, 43, 47, 49, 51, 53, 57, 59, 61, 63, 67, 69, 71, 73, 77, 79, 81, 83, 87, 89, 91, 93, 97, 99

Offset: 1

Zak Seidov, Jul 04 2003

This is a finite sequence which contains the first few terms of A045572.

Smallest prime > A085820(n) ending with A085820(n) in A085821.

Caldwell and Honaker, Prime Curios!: NASCAR Prime Puzzle

Cf. A085821.

Mod[Prime[Range[5,1000]],100]//Union (* Harvey P. Dale, Jul 10 2017 *)

[x for x in range(100) if kronecker(x^2,100)==1] # Zerinvary Lajos, Dec 07 2009

A337834 If k is the n-th number ending in 1,3,7, or 9, a(n) is the least prime > k ending in k.

Original entry on oeis.org

11, 13, 17, 19, 211, 113, 317, 419, 421, 223, 127, 229, 131, 233, 137, 139, 241, 443, 347, 149, 151, 353, 157, 359, 461, 163, 167, 269, 271, 173, 277, 179, 181, 283, 487, 389, 191, 193, 197, 199, 5101, 1103, 5107, 1109, 2111, 2113, 1117, 3119, 3121, 1123, 4127, 1129, 2131, 4133, 2137, 4139, 2141

Offset: 1

Robert Israel, Sep 24 2020

a(n) exists by Dirichlet's theorem on primes in arithmetic progressions.

			For n=3 the third number ending in 1,3,7 or 9 is 7 and the least prime > 7 ending in 7 is a(3)=17.
For n=12 the 12th number ending in 1,3,7 or 9 is 29 and the least prime > 29 ending in 29 is a(12)=229.

Robert Israel, Table of n, a(n) for n = 1..10000
Index entries for primes involving decimal expansion of n

Cf. A085821, A338715.

f:= proc(n) local d, x;
  d:= ilog10(n)+1;
  for x from n + 10^d by 10^d do
    if isprime(x) then return x fi
  od
end proc:
map(f, [seq(seq(10*i+j, j=[1,3,7,9]),i=0..99)];

cp's OEIS Frontend

A085820 Possible two-digit endings of primes (with leading zeros).

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