A067354 Numbers k such that prime(k+2)-(k+2)*tau(k+2) = prime(k-2)-(k-2)*tau(k-2) where tau(k) = A000005(k) is the number of divisors of k.

3, 8, 30, 68, 277, 600, 1444, 2123, 3128, 3230, 3672, 3783, 4441, 5016, 5052, 5144, 5304, 5665, 6353, 6468, 6513, 6588, 6772, 6983, 7044, 7087, 8392, 8418, 8632, 8866, 9217, 9264, 9292, 9540, 9917, 9949, 10495, 11429, 11532, 13474, 14063, 15431

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Mathematica

Select[Range[3, 16000], Prime[#-2]-(#-2)DivisorSigma[0, #-2]==Prime[#+2]-(#+2)DivisorSigma[0, #+2]&] (* Harvey P. Dale, Dec 20 2015 *)

Prog

(PARI) f(n) = prime(n) - n * numdiv(n);
is(n) = n > 2 &&  f(n-2) == f(n+2); \\ Amiram Eldar, Apr 16 2024

Crossrefs

Cf. A000005, A067292, A067293, A067335, A067355, A067356.

Sequence in context: A289486 A245361 A247340 * A344899 A148877 A148878

Adjacent sequences: A067351 A067352 A067353 * A067355 A067356 A067357

Keyword

easy,nonn

Author

Benoit Cloitre, Feb 24 2002

Status

approved