A031938 Lower prime of a difference of 20 between consecutive primes.

887, 1637, 3089, 3413, 3947, 5717, 5903, 5987, 6803, 7649, 8243, 8543, 8783, 8867, 9257, 10223, 10433, 10667, 11027, 11093, 11177, 11447, 11597, 11657, 11867, 11987, 13127, 13421, 13649, 14087, 14177, 15473, 16943, 17519, 17807, 18149, 18461, 18617, 18839

Offset: 1

Author

Jeff Burch

Keywords

• nonn

Examples

			887 is a term as the next prime is 907.
		

Links

• Remi Eismann, Table of n, a(n) for n = 1..10000
• Index entries for primes, gaps between

Programs

Magma

[p: p in PrimesUpTo(20000) | NextPrime(p)-p eq 20]; // Bruno Berselli, Apr 09 2013

Mathematica

(*M6*) a=887; S={}; Do[b=NextPrime[a]; If[b-a==20,AppendTo[S,a]]; a=b,{10^4}]; S (* Zak Seidov, Aug 14 2009 *)
Transpose[Select[Partition[Prime[Range[2000]], 2, 1], Last[#] - First[#] == 20 &]][[1]] (* Bruno Berselli, Apr 09 2013 *)

Formula

a(n) = prime(A320708(n)). - R. J. Mathar, Apr 30 2024

Extensions

Entries and b-file checked by Zak Seidov, Aug 14 2009