

A212955


Least k such that k*30^n1 and k*30^n+1 are twin primes.


2



1, 7, 19, 44, 52, 19, 8, 77, 82, 40, 14, 140, 44, 119, 592, 217, 272, 744, 737, 536, 1298, 219, 839, 977, 226, 773, 576, 1111, 461, 130, 104, 1152, 2083, 721, 587, 6312, 2126, 489, 331, 6008, 4582, 420, 14, 3951, 432, 2703, 4498, 2219, 1029, 1411, 2392, 3431
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OFFSET

1,2


LINKS

Pierre CAMI, Table of n, a(n) for n = 1..270


EXAMPLE

1*30^11 = 29 is prime and 1*30^1+1 = 31 is prime. Hence a(1) = 1.


MATHEMATICA

Table[k = 1; While[! PrimeQ[k*30^n + 1]  ! PrimeQ[k*30^n  1], k++]; k, {n, 60}] (* T. D. Noe, Jun 01 2012 *)
tpk[n_]:=Module[{k=1, c=30^n}, While[!AllTrue[k*c+{1, 1}, PrimeQ], k++]; k]; Array[tpk, 60] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 26 2015 *)


PROG

PFGW64 and SCRIPTIFY from Primeform Group
command : pfgw64 f in.txt
in.txt file :
SCRIPT
DIM nn, 0
DIM kk, 0
DIMS tt
OPENFILEOUT myfile, a(n).txt
LABEL loopn
SET nn, nn+1
IF nn>270 THEN END
SET kk, 0
LABEL loopk
SET kk, kk+1
SETS tt, %d, %d\,; nn; kk
PRP kk*30^nn1, tt
IF ISPRP THEN GOTO a
IF ISPRIME THEN GOTO a
GOTO loopk
LABEL a
PRP kk*30^nn+1, tt
IF ISPRP THEN GOTO b
IF ISPRIME THEN GOTO b
GOTO loopk
LABEL b
WRITE myfile, tt
GOTO loopn


CROSSREFS

Sequence in context: A113927 A155399 A268926 * A155415 A155273 A277613
Adjacent sequences: A212952 A212953 A212954 * A212956 A212957 A212958


KEYWORD

nonn


AUTHOR

Pierre CAMI, Jun 01 2012


STATUS

approved



