A189314 Nonprimes k such that 2*omega(4k) = omega(4k+2), where omega(j) is the number of distinct primes dividing j, A001221.

1, 4, 8, 52, 82, 128, 136, 142, 172, 178, 192, 214, 232, 262, 292, 304, 332, 346, 352, 382, 388, 412, 448, 472, 478, 484, 500, 502, 542, 556, 586, 592, 604, 622, 632, 640, 652, 676, 712, 724, 752, 766, 772, 802, 808, 832, 838, 841, 862, 864, 916, 922, 934

Offset

1,2

Links

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Maple

Omega:=proc(n)return nops(factorset(n)):end:for n from 1 to 1000 do
if(not isprime(n) and 2*Omega(4*n)=Omega(4*n+2))then printf("%d, ", n); fi:od: # Nathaniel Johnston, Apr 19 2011

Mathematica

Select[Range[1000], ! PrimeQ[#] && 2*PrimeNu[4 #] == PrimeNu[4 # + 2] &] (* T. D. Noe, Apr 21 2011 *)

Crossrefs

Cf. A189313 (prime version of this sequence).

Sequence in context: A329942 A056397 A369074 * A358791 A215746 A128893

Adjacent sequences: A189311 A189312 A189313 * A189315 A189316 A189317

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 19 2011

Status

approved