A224491 Smallest k such that k*2*p(n)^2-1=q is prime k*2*q^2-1=r k*2*r^2-1=s, r and s are also prime.

705, 1, 306, 390, 2539, 526, 1939, 439, 7048, 286, 561, 985, 90, 2385, 2089, 328, 2266, 664, 4245, 2451, 453, 391, 411, 406, 4068, 4975, 8151, 199, 834, 4423, 169, 76, 5710, 861, 3930, 1659, 1246, 2838, 750, 153, 8664, 3730, 1195, 7815, 1746, 1735, 594, 985

Offset

1,1

Links

Pierre CAMI, Table of n, a(n) for n = 1..5600

Mathematica

a[n_] := For[k = 1, True, k++, p = Prime[n]; If[PrimeQ[q = k*2*p^2 - 1] && PrimeQ[r = k*2*q^2 - 1] && PrimeQ[k*2*r^2 - 1], Return[k]]]; Table[a[n], {n, 1, 48}] (* Jean-François Alcover, Apr 12 2013 *)

Prog

(PFGW & SCRIPTIFY)
SCRIPT
DIM k
DIM i, 0
DIM q
DIMS t
OPENFILEOUT myf, a(n).txt
LABEL a
SET i, i+1
IF i>5600 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 GOTO d
GOTO b
LABEL d
SET q, k*2*q^2-1
PRP q, t
IF ISPRP THEN WRITE myf, t
IF ISPRP THEN GOTO e
GOTO b

Crossrefs

Cf. A224489, A224490, A224492.

Sequence in context: A185569 A238322 A091553 * A126830 A005845 A183795

Adjacent sequences: A224488 A224489 A224490 * A224492 A224493 A224494

Keyword

nonn

Author

Pierre CAMI, Apr 08 2013

Extensions

Typo in name fixed by Zak Seidov, Apr 11 2013

Status

approved