A067335 Numbers k such that prime(k+1)-(k+1)*tau(k+1) = prime(k-1)-(k-1)*tau(k-1) where tau(k) = A000005(k) is the number of divisors of k.

202, 216, 471, 583, 816, 850, 894, 905, 922, 1277, 1335, 1386, 1594, 1712, 1774, 1942, 1958, 2554, 2760, 2777, 2840, 2876, 2934, 2944, 3132, 3438, 3566, 3694, 3900, 3980, 4013, 4188, 4342, 4352, 4526, 4594, 4627, 4686, 4808, 5268, 5730, 6032, 6326

Offset

1,1

Links

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

Mathematica

f[n_] := f[n] = Prime[n] - n * DivisorSigma[0, n]; Select[Range[2, 6500], f[#+1] == f[#-1] &] (* Amiram Eldar, Apr 08 2024 *)

Prog

(PARI) f(n) = prime(n) - n * numdiv(n);
is(n) = n > 1 && f(n+1) == f(n-1); \\ Amiram Eldar, Apr 08 2024

Crossrefs

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

Sequence in context: A216376 A166505 A066130 * A356881 A235082 A260280

Adjacent sequences: A067332 A067333 A067334 * A067336 A067337 A067338

Keyword

easy,nonn

Author

Benoit Cloitre, Feb 24 2002

Status

approved