A156541 Multiplicative closure of Sophie Germain primes (A005384).

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 15, 16, 18, 20, 22, 23, 24, 25, 27, 29, 30, 32, 33, 36, 40, 41, 44, 45, 46, 48, 50, 53, 54, 55, 58, 60, 64, 66, 69, 72, 75, 80, 81, 82, 83, 87, 88, 89, 90, 92, 96, 99, 100, 106, 108, 110, 113, 115, 116, 120, 121, 123, 125, 128, 131, 132

Offset: 1

Author

Reinhard Zumkeller, Feb 10 2009

Keywords

• nonn

Comments

A156542(a(n)) = A001221(a(n));

Subsequence of A130176.

Links

• R. Zumkeller, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A156541, A156543.

Programs

Mathematica

Select[Range@132, And @@ PrimeQ[FactorInteger[#][[All, 1]]*2 + 1] &] (* Ivan Neretin, Aug 30 2015 *)