A224905 Smallest k such that (10^n+k, 10^n+k+2) and (10^(n+1)+k, 10^(n+1)+k+2) are two pairs of twin primes.

1, 49, 91, 1117, 2929, 721, 1819, 37237, 30979, 30967, 29629, 6457, 53269, 27727, 271159, 556651, 190489, 62797, 105259, 784777, 290659, 1320829, 438037, 1019317, 333991, 248371, 226609, 671227, 384571, 1573537, 366841, 954391, 1701247, 540811, 1105291

Offset

1,2

Links

Pierre CAMI, Table of n, a(n) for n = 1..76

Example

10^1+1=11 prime as 13 10^2+1=101 prime as 103 so a(1)=1.

Mathematica

sk[n_]:=Module[{k=1}, While[!AllTrue[{10^n+k, 10^n+k+2, 10^(n+1)+k, 10^(n+1)+k+2}, PrimeQ], k++]; k]; Array[sk, 35] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 09 2020 *)

Prog

PFGW & SCRIPTIFY
SCRIPT
DIM n, 0
DIM k, -1
DIMS t
OPENFILEOUT myf, a(n).txt
LABEL a
SET n, n+1
SET k, -1
LABEL b
SET k, k+2
SETS t, %d, %d\,; n; k
PRP 10^n+k, t
IF ISPRP THEN GOTO c
GOTO b
LABEL c
PRP 10^n+k+2, t
IF ISPRP THEN GOTO d
GOTO b
LABEL d
PRP 10^(n+1)+k, t
IF ISPRP THEN GOTO e
GOTO b
LABEL e
PRP 10^(n+1)+k+2, t
IF ISPRP THEN GOTO f
GOTO b
LABEL f
WRITE myf, t
SET k, k+2
GOTO a

Crossrefs

Cf. A124001, A224846.

Sequence in context: A084632 A020176 A146064 * A224846 A260469 A275419

Adjacent sequences: A224902 A224903 A224904 * A224906 A224907 A224908

Keyword

nonn

Author

Pierre CAMI, Jul 25 2013

Status

approved