A334141 Numbers that are the product of distinct twin primes.

1, 3, 5, 7, 11, 13, 15, 17, 19, 21, 29, 31, 33, 35, 39, 41, 43, 51, 55, 57, 59, 61, 65, 71, 73, 77, 85, 87, 91, 93, 95, 101, 103, 105, 107, 109, 119, 123, 129, 133, 137, 139, 143, 145, 149, 151, 155, 165, 177, 179, 181, 183, 187, 191, 193, 195, 197, 199

Offset: 1

Author

Ilya Gutkovskiy, Apr 15 2020

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Twin Primes

Crossrefs

Subsequence of A005117.

Cf. A001097, A037074, A048599, A074480, A073485.

Programs

Maple

N:= 1000: # for terms <= N
P:= select(isprime, {seq(i,i=3..N+2,2)}):
TP:= P intersect map(`+`,P,2):
TP:= map(t -> (t-2,t), TP):
TP:= sort(convert(TP,list)):
S:= {1}:
for i from 1 to nops(TP) do
  S0:= S;
  S:= S union map(`*`, select(`<=`,S,N/TP[i]),TP[i]);
od:
sort(convert(S,list)); # Robert Israel, Oct 28 2020