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

1,1

Links

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

Example

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

Mathematica

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

Prog

(Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [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

Crossrefs

Cf. A001358, A065516, A217030.

Sequence in context: A252203 A252202 A236594 * A243993 A157613 A233899

Adjacent sequences: A217332 A217333 A217334 * A217336 A217337 A217338

Keyword

nonn

Author

Zak Seidov, Oct 01 2012

Status

approved