A172187 - OEIS

A172187

Numbers k such that k and k+1 are squarefree but 2*k+1 is not.

13, 22, 37, 58, 73, 85, 94, 122, 130, 137, 157, 166, 181, 193, 202, 229, 237, 238, 253, 262, 265, 301, 302, 310, 318, 346, 373, 382, 409, 418, 433, 437, 445, 454, 462, 465, 481, 514, 517, 526, 537, 541, 553, 562, 589, 598, 634, 661, 662, 670, 697, 706, 733

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

MATHEMATICA

Select[Range[750], And @@ SquareFreeQ /@ {#, # + 1} && !SquareFreeQ[2# + 1] &] (* Amiram Eldar, Mar 22 2020 *)

CROSSREFS

Complement of A007674 and A172186.

Sequence in context: A164504 A162245 A159302 * A164412 A164472 A164446

Adjacent sequences: A172184 A172185 A172186 * A172188 A172189 A172190

KEYWORD

nonn

AUTHOR

Artur Jasinski, Jan 28 2010

STATUS

approved