A234499 - OEIS

A234499

Primes of the form (p*q*r*s - 1)/2, where p, q, r,s are distinct primes.

577, 997, 1567, 1627, 1657, 2467, 2557, 2593, 3391, 3517, 3547, 3607, 3697, 3727, 3877, 4231, 4273, 4357, 4933, 5167, 5227, 5347, 5407, 5527, 5857, 5869, 6121, 6451, 7297, 7417, 7927, 8053, 8179, 8389, 8431, 8521, 8627, 8677, 9091, 9397, 9439, 9547, 9613

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OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..100

EXAMPLE

(See A234498.)

MATHEMATICA

t = Select[Range[1, 20000, 2], Map[Last, FactorInteger[#]] == Table[1, {4}] &]; Take[(t - 1)/2, 120] (* A234105 *)

v = Flatten[Position[PrimeQ[(t - 1)/2], True]] ; w = Table[t[[v[[n]]]], {n, 1, Length[v]}] (* A234498 *)

(w - 1)/2 (* A234499 *) (* Peter J. C. Moses, Dec 23 2013 *)

Module[{upto=10000, maxp}, maxp=Ceiling[PrimePi[upto/30]]; Select[Sort[ Select[ (#-1)/2&/@Times@@@Subsets[Prime[Range[maxp]], {4}], PrimeQ]], #<=upto&]] (* Harvey P. Dale, Feb 07 2016 *)

CROSSREFS

Cf. A234105, A234499, A234500.

Sequence in context: A198777 A104937 A234105 * A218039 A218157 A158370

Adjacent sequences: A234496 A234497 A234498 * A234500 A234501 A234502

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jan 01 2014

STATUS

approved