A189763 Even numbers n such that solutions to x' = n are not all semiprimes, where x' denotes the arithmetic derivative (A003415).

12, 16, 24, 32, 44, 48, 56, 60, 68, 72, 80, 92, 96, 108, 112, 120, 124, 128, 140, 152, 156, 162, 164, 168, 176, 188, 192, 212, 216, 220, 236, 240, 244, 248, 252, 272, 284, 288, 296, 316, 318, 320, 324, 332, 336, 350, 356, 360, 368, 378, 380, 384, 392, 408

Offset

1,1

Comments

It appears that the anti-derivatives of even numbers n are overwhelmingly semiprimes of the form (n/2)^2 - k^2. For example, 1000 has 28 anti-derivatives, all semiprimes.

Links

Table of n, a(n) for n=1..54.

Crossrefs

Cf. A003415, A189762, A189764.

Sequence in context: A335224 A335244 A330546 * A077617 A182074 A192609

Adjacent sequences: A189760 A189761 A189762 * A189764 A189765 A189766

Keyword

nonn

Author

T. D. Noe, Apr 27 2011

Status

approved