A358130 Indices k such that A358128(k) is a square.

1, 2, 3, 6, 9, 11, 15, 45, 51, 59, 81, 126, 165, 174, 179, 255, 681, 831, 839, 921, 1734, 1739, 1845, 2499, 2519, 2661, 3119, 5061, 5094, 5099, 5289, 5301, 8061, 8571, 8579, 9654, 9659, 11094, 11399, 12315, 13254, 16011, 16379, 18225, 18234, 18239, 19401, 19689, 26214, 26219, 27141, 28554, 29039

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..870

Example

a(5) = 9 is a term because A358128(9) = 25 = 5^2 is a square.

Maple

f:= proc(n) local p;
  p:= 1:
  do
    p:= nextprime(p);
    if isprime(p+4*n) and numtheory:-bigomega(p+2*n) = 2 then return p+2*n fi
  od
end proc:
select(t -> issqr(f(t)), [$1..30000]);

Prog

(PARI) isok(k) = my(x=2*k+2); while ((bigomega(x)!=2) || !isprime(x-2*k) || !isprime(x+2*k), x++); issquare(x); \\ Michel Marcus, Oct 31 2022

Crossrefs

Cf. A358128.

Sequence in context: A067886 A227000 A338546 * A176189 A057127 A224449

Adjacent sequences: A358127 A358128 A358129 * A358131 A358132 A358133

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Oct 30 2022

Status

approved