

A224490


Smallest k such that k*2*p(n)^21=q is prime and k*2*q^21 is also prime.


9



1, 1, 25, 9, 21, 3, 1, 16, 25, 136, 10, 33, 90, 250, 10, 55, 1, 9, 36, 75, 1, 4, 33, 406, 103, 15, 121, 4, 244, 78, 28, 19, 49, 105, 45, 34, 10, 46, 33, 4, 111, 15, 9, 36, 118, 66, 10, 13, 31, 76, 66, 36, 55, 15, 4, 48, 6, 66, 13, 34, 54, 64, 153, 1, 60, 48
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OFFSET

1,3


LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10000


EXAMPLE

1*2*2^21=7 prime q 1*2*7^21=97 also prime so a(1)=1.


MATHEMATICA

a[n_] := For[k = 1, True, k++, p = Prime[n]; If[PrimeQ[q = k*2*p^2  1] && PrimeQ[k*2*q^2  1], Return[k]]]; Table[a[n], {n, 1, 66}] (* JeanFrançois Alcover, Apr 12 2013 *)


PROG

SCRIPT
DIM k
DIM i, 0
DIM q
DIMS t
OPENFILEOUT myf, a(n).txt
LABEL a
SET i, i+1
IF i>20000 THEN END
SET k, 0
LABEL b
SET k, k+1
SETS t, %d, %d, %d\,; k; i; p(i)
SET q, k*2*p(i)^21
PRP q, t
IF ISPRP THEN GOTO c
GOTO b
LABEL c
SET q, k*2*q^21
PRP q, t
IF ISPRP THEN WRITE myf, t
IF ISPRP THEN GOTO a
GOTO b


CROSSREFS

Cf. A224489, A224491, A224492.
Sequence in context: A065910 A096521 A215539 * A226224 A181763 A171638
Adjacent sequences: A224487 A224488 A224489 * A224491 A224492 A224493


KEYWORD

nonn


AUTHOR

Pierre CAMI, Apr 08 2013


EXTENSIONS

Typo in name fixed by Zak Seidov, Apr 11 2013


STATUS

approved



