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A225941 Smallest k such that k*6^n-1 is prime 2
1, 2, 2, 2, 2, 3, 5, 13, 3, 19, 5, 2, 3, 28, 12, 2, 15, 19, 19, 20, 7, 13, 5, 3, 4, 2, 2, 7, 42, 7, 4, 7, 5, 34, 8, 2, 78, 13, 12, 2, 3, 24, 4, 12, 2, 37, 30, 5, 2, 28, 12, 2, 2, 35, 59, 58, 15, 65, 82, 28, 32, 60, 10, 48, 8, 14, 23, 5, 32, 18, 3, 80, 28, 12, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
In average k~0.6*n and 0<k<8*n until a proof k may be >8*n
LINKS
MATHEMATICA
skp[n_]:=Module[{k=1, c=6^n}, While[!PrimeQ[k*c-1], k++]; k]; Array[skp, 80] (* Harvey P. Dale, Jul 22 2013 *)
PROG
(PFGW & SCRIPTIFY)
SCRIPT
DIM n, 0
DIM k
DIMS t
OPENFILEOUT myf, a(n).txt
LABEL a
SET n, n+1
IF n>3000 THEN END
SET k, 0
LABEL b
SET k, k+1
SETS t, %d, %d\,; n; k
PRP k*6^n-1, t
IF ISPRP THEN GOTO c
GOTO b
LABEL c
WRITE myf, t
GOTO a
(PARI) a(n) = my(k=1); while (!isprime(k*6^n-1), k++); k; \\ Michel Marcus, Sep 16 2019
CROSSREFS
Cf. A225911.
Sequence in context: A356758 A098133 A138185 * A138705 A333528 A319187
KEYWORD
nonn
AUTHOR
Pierre CAMI, May 21 2013
STATUS
approved

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)