A104783 Prime numbers p such that pi(p) + 2*p is a square.

43, 113, 331, 1019, 1559, 1613, 2087, 2551, 3217, 5471, 6317, 7109, 7583, 7703, 11777, 13967, 15649, 18353, 21277, 22921, 24847, 27767, 27997, 29167, 66617, 86531, 91081, 91921, 112289, 116041, 122267, 122753, 123727, 125197, 138289

Offset

1,1

Links

Table of n, a(n) for n=1..35.

Formula

a(n) = prime(A104776(n)).

Mathematica

Select[Prime[Range[13000]], IntegerQ[Sqrt[PrimePi[#]+2 #]]&] (* Harvey P. Dale, Jun 01 2021 *)

Prog

(PARI) lista(nn) = {vec = vector(nn, i, prime(i)); pp = select(i->(issquare(2*i+primepi(i))), vec); pp; } \\ Michel Marcus, Oct 09 2013

Crossrefs

Cf. A104776.

Sequence in context: A052089 A260809 A039471 * A142081 A138695 A297412

Adjacent sequences: A104780 A104781 A104782 * A104784 A104785 A104786

Keyword

nonn

Author

Zak Seidov, Apr 23 2005

Status

approved