A067356 Numbers k such that prime(k+3)-(k+3)*tau(k+3) = prime(k)-k*tau(k) where tau(k) = A000005(k) is the number of divisors of k.

172, 206, 435, 542, 551, 575, 611, 626, 718, 759, 903, 955, 1102, 1238, 1495, 1711, 2009, 2379, 2385, 2482, 2572, 2815, 2874, 3018, 3103, 3222, 3225, 3802, 3899, 4055, 4335, 4342, 4430, 4439, 4545, 4682, 5154, 5183, 5467, 5594, 6036, 6058, 6202, 6231

Offset

1,1

Links

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

Mathematica

ptQ[n_]:=Module[{n3=n+3}, Prime[n3]-(n3)DivisorSigma[0, n3]==Prime[n]- n*DivisorSigma[ 0, n]]; Select[Range[6300], ptQ] (* Harvey P. Dale, Jul 22 2012 *)

Prog

(PARI) f(n) = prime(n) - n * numdiv(n);
is(n) = n > 3 && f(n) == f(n+3); \\ Amiram Eldar, Apr 08 2024

Crossrefs

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

Sequence in context: A223823 A224555 A146339 * A230371 A056132 A261706

Adjacent sequences: A067353 A067354 A067355 * A067357 A067358 A067359

Keyword

easy,nonn

Author

Benoit Cloitre, Feb 24 2002

Status

approved