A234093 - OEIS

A234093

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

7, 10, 16, 17, 19, 25, 27, 28, 32, 34, 38, 42, 43, 45, 46, 47, 55, 57, 59, 61, 64, 66, 70, 71, 72, 77, 79, 80, 88, 91, 92, 93, 100, 101, 102, 104, 106, 107, 108, 109, 110, 117, 118, 123, 124, 126, 129, 132, 133, 143, 145, 147, 149, 150, 151, 152, 154, 159

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OFFSET

1,1

COMMENTS

A102770 is subsequence. - Zak Seidov, Feb 21 2014

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

(3*5 - 1)/2 = 7; (3*7 - 1)/2 = 10.

MATHEMATICA

t = Select[Range[1, 7000, 2], Map[Last, FactorInteger[#]] == Table[1, {2}] &]; Take[(t - 1)/2, 120] (* A234093 *)

v = Flatten[Position[PrimeQ[(t - 1)/2], True]] ; w = Table[t[[v[[n]]]], {n, 1, Length[v]}] (* A233561 *)