A342648 Composite numbers k such that k-A238525(k) and k+A238525(k) are prime.

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

Robert Israel, Table of n, a(n) for n = 1..10000

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

Adjacent sequences: A342645 A342646 A342647 * A342649 A342650 A342651

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Mar 17 2021

Status

approved