A177222 Numbers k that are the products of two distinct primes, such that 2*k + 1 and 4*k + 3 are also products of two distinct primes.

38, 46, 106, 129, 133, 145, 201, 203, 235, 291, 298, 334, 335, 381, 407, 417, 458, 489, 497, 538, 579, 583, 597, 623, 626, 649, 685, 689, 694, 707, 758, 767, 781, 815, 898, 899, 921, 926, 959, 995, 1073, 1079, 1082, 1094, 1099, 1139, 1142, 1157, 1214, 1226

Offset

1,1

Links

Table of n, a(n) for n=1..50.

Example

38 is a term because 38 = 2*19, 2*38 + 1 = 77 = 7*11, and 4*38 + 1 = 155 = 5*31.

Mathematica

f[n_] := Last/@FactorInteger[n] == {1, 1};  lst = {}; Do[If[f[n] && f[2*n+1] && f[4*n+3], AppendTo[lst, n]], {n, 1000}]; lst

Crossrefs

Cf. A006881, A111153, A177210, A177211, A177212, A177213, A177214, A177215, A177216, A177217, A177220, A177221.

Cf. A133123 (allows squares also).

Sequence in context: A078550 A295491 A133123 * A078539 A282813 A125970

Adjacent sequences: A177219 A177220 A177221 * A177223 A177224 A177225

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 05 2010

Status

approved