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 A224490 Smallest k such that k*2*p(n)^2-1=q is prime and k*2*q^2-1 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Pierre CAMI, Table of n, a(n) for n = 1..10000 EXAMPLE 1*2*2^2-1=7 prime q 1*2*7^2-1=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}] (* Jean-François 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)^2-1 PRP q, t IF ISPRP THEN GOTO c GOTO b LABEL c SET q, k*2*q^2-1 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

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)