A217335 Semiprimes p such that next semiprime after p is p+20.

2681, 3523, 6953, 8227, 16817, 26101, 28533, 28563, 28617, 29011, 34249, 37007, 42401, 49983, 50117, 55703, 60657, 65083, 66938, 71381, 71873, 73443, 76247, 92773, 92978, 101109, 101271, 109129, 111479, 112051, 113018, 113721, 115586, 116267, 119969, 124177

Offset: 1

Author

Zak Seidov, Oct 01 2012

Keywords

• nonn

Examples

			2681 = A001358(760)  = 7*383, 2701 = A001358(761) = 37*73,
3523 = A001358(986)  = 13*271, 3543 = A001358(987) = 3*1181.
		

Links

• Zak Seidov, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A001358, A065516, A217030.

Programs

Magma

IsSemiprime:=func; [n: n in [4..130000] | IsSemiprime(n) and IsSemiprime(n+20) and forall{n+i: i in [1..19] | not IsSemiprime(n+i)}]; // Bruno Berselli, Oct 01 2012

Mathematica

f = Flatten@Position[Differences@(s = Select[Range@100000, PrimeOmega@# == 2 &]), 20]; s[[f]] (* Hans Rudolf Widmer, Aug 19 2024 *)