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A334141
Numbers that are the product of distinct twin primes.
1
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
1,2
LINKS
Eric Weisstein's World of Mathematics, Twin Primes
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
CROSSREFS
Subsequence of A005117.
Sequence in context: A056911 A152955 A235866 * A325570 A210719 A353685
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 15 2020
STATUS
approved