A181793 - OEIS

%I #8 Mar 30 2012 17:27:19

%S 28,52,76,124,148,172,175,244,268,292,316,325,388,412,436,475,508,556,

%T 604,628,652,724,772,775,796,844,847,892,916,925,964,1075,1084,1108,

%U 1132,1228,1252,1324,1348,1396,1468,1492,1516,1525,1573,1588,1636,1675,1684,1732,1756,1825,1828,1852,1948,1975,1996

%N Primitive members of A181792.

%C A member of A181792 is called primitive iff it is not a multiple of any smaller member of A181792.  Every member of A181792 is a multiple of at least one member of this sequence.

%C Equivalently, positive integers of the form p*q^2, where p is a prime congruent to 1 mod 3 and q is a prime congruent to 2 mod 6.

%e Of 28's 6 divisors, 4 (1, 4, 7, and 28) are congruent to 1 mod 3; 2 (2 and 14) are congruent to 2 mod 3; and 0 are congruent to 0 mod 3.  Note that 4, 2, and 0 are congruent to 1 mod 3, 2 mod 3, and 0 mod 3 respectively. 28 therefore belongs to A181792.  Since no smaller divisor of 28 belongs to A181792, 28 also belongs to this sequence.

%Y Subsequence of A054753.

%K nonn

%O 1,1

%A _Matthew Vandermast_, Nov 13 2010