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A342648
Composite numbers k such that k-A238525(k) and k+A238525(k) are prime.
1
6, 10, 12, 22, 142, 274, 382, 694, 862, 922, 2122, 2182, 2962, 3334, 3862, 4054, 4282, 4474, 5374, 6514, 6742, 6934, 7534, 7702, 8254, 8482, 8674, 8962, 10042, 10834, 11734, 13402, 13654, 14254, 14662, 14914, 15094, 15514, 15754, 16462, 17074, 18022, 18874, 19714, 20074, 20182, 22234, 23434
OFFSET
1,1
COMMENTS
If p, p+2 and 3*p-2 are prime then 2*p is a term.
Is 12 the only term not of this form?
LINKS
EXAMPLE
a(4) = 22 is a term because A238525(22) = 9 and 22-9 = 13 and 22+9 = 31 are prime.
MAPLE
filter:= proc(n) local t, s, r;
if isprime(n) then return false fi;
s:= add(t[1]*t[2], t=ifactors(n)[2]);
r:= n mod s;
isprime(n+r) and isprime(n-r);
end proc:
select(filter, [$4..10^5]);
CROSSREFS
Cf. A238525.
Sequence in context: A315139 A046363 A101086 * A297620 A074924 A064166
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Mar 17 2021
STATUS
approved