A234372 Second smallest prime congruent to 1 modulo n-th prime.

5, 13, 31, 43, 67, 79, 137, 229, 139, 233, 373, 223, 739, 431, 659, 743, 827, 733, 1609, 853, 439, 1423, 499, 1069, 971, 809, 1031, 857, 2399, 1583, 2287, 787, 1097, 1669, 1789, 1511, 3769, 2609, 5011, 1039, 1433, 1811, 2293, 1931, 4729, 2389, 4643, 6691, 5903, 5039, 1399, 1913, 2411, 4519, 9767, 5261, 3229, 2711

Offset: 1

Author

Zak Seidov, Dec 25 2013

Keywords

• nonn

Comments

a(10^k) for k=1..10: 233, 11903, 142543, 837833, 36391853, 247773809, 3947342807, 146741381497, 684052904671, 16638454841119.

Examples

			a(3) = 31 because prime(3) = 5, first prime == 1 (mod 5) is 11 and 2nd one is 31.
a(4) = 43 because prime(4) = 7, first prime == 1 (mod 7) is 29 and 2nd one is 43.
		

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A035095.

Programs

Mathematica

Table[If[n<2,5,p=Prime[n];r=1+2*p;While[!PrimeQ[r],r+=2*p];r+=2*p;While[!PrimeQ[r],r+=2*p];r],  {n,100}]