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A064504 Numbers k such that prime(k) + prime(k+1)*2 is a square. 1
9, 96, 461, 548, 565, 876, 1053, 1202, 1302, 1426, 1596, 2040, 3040, 4392, 5710, 6960, 7749, 7988, 8630, 8818, 9323, 9505, 10465, 11617, 11828, 12674, 13119, 17580, 18507, 18954, 22922, 23197, 25821, 33502, 35877, 37065, 37321 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MATHEMATICA
okQ[list_]:=IntegerQ[Sqrt[First[list]+2Last[list]]];
PrimePi/@Transpose[Select[Partition[Prime[Range[40000]], 2, 1], okQ]][[1]]
(* Harvey P. Dale, Mar 05 2011 *)
PROG
(PARI) for(n=1, 10^6, if(issquare(prime(n)+prime(n+1)*2), print1(n, " ")))
(PARI) { n=0; default(primelimit, 21000000); for (m=1, 10^9, if (issquare(prime(m) + 2*prime(m + 1)), write("b064504.txt", n++, " ", m); if (n==175, break)) ) } \\ Harry J. Smith, Sep 16 2009
CROSSREFS
Sequence in context: A065456 A052389 A197665 * A090448 A264219 A005545
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Oct 06 2001
EXTENSIONS
Offset changed from 0 to 1 by Harry J. Smith, Sep 16 2009
STATUS
approved

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Last modified April 13 02:05 EDT 2024. Contains 371639 sequences. (Running on oeis4.)