A234105 Integers of the form (p*q*r*s - 1)/2, where p, q, r, s are distinct primes.

577, 682, 892, 997, 1072, 1207, 1402, 1501, 1522, 1567, 1627, 1657, 1852, 1897, 1942, 1963, 2152, 2194, 2242, 2257, 2320, 2392, 2422, 2467, 2502, 2557, 2593, 2656, 2782, 2827, 2932, 3022, 3052, 3097, 3139, 3202, 3272, 3277, 3349, 3382, 3391, 3517, 3547, 3580

Offset

1,1

Links

Table of n, a(n) for n=1..44.

Formula

-1 + A234500.

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 *)

Crossrefs

Cf. A234498, A234499, A234500, A234093, A234097.

Sequence in context: A198778 A198777 A104937 * A234499 A218039 A218157

Adjacent sequences: A234102 A234103 A234104 * A234106 A234107 A234108

Keyword

nonn,easy

Author

Clark Kimberling, Jan 01 2014

Status

approved