A368696 Numbers whose arithmetic derivative (A003415) is a squarefree number of the form 4k+2.

9, 21, 25, 33, 49, 57, 69, 85, 93, 121, 129, 133, 145, 161, 169, 177, 185, 201, 205, 209, 213, 217, 221, 237, 249, 253, 265, 289, 305, 309, 315, 321, 341, 361, 365, 377, 381, 393, 413, 417, 437, 445, 453, 469, 485, 489, 493, 495, 497, 501, 505, 517, 529, 537, 545, 553, 565, 573, 597, 633, 649, 669, 681, 685, 689

Offset: 1

Author

Antti Karttunen, Jan 09 2024

Keywords

• nonn

Crossrefs

Intersection of A327862 and A328393.

Cf. A003415, A005117, A368697 (subsequence).

Programs

PARI

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
isA368696(n) = { my(d=A003415(n)); ((2==(d%4))&&issquarefree(d)); };