

A339004


Numbers of the form prime(x) * prime(y) where x and y are distinct and both even.


13



21, 39, 57, 87, 91, 111, 129, 133, 159, 183, 203, 213, 237, 247, 259, 267, 301, 303, 321, 339, 371, 377, 393, 417, 427, 453, 481, 489, 497, 519, 543, 551, 553, 559, 579, 597, 623, 669, 687, 689, 703, 707, 717, 749, 753, 789, 791, 793, 813, 817, 843, 879, 917
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OFFSET

1,1


COMMENTS



LINKS



FORMULA



EXAMPLE

The sequence of terms together with their prime indices begins:
21: {2,4} 267: {2,24} 543: {2,42}
39: {2,6} 301: {4,14} 551: {8,10}
57: {2,8} 303: {2,26} 553: {4,22}
87: {2,10} 321: {2,28} 559: {6,14}
91: {4,6} 339: {2,30} 579: {2,44}
111: {2,12} 371: {4,16} 597: {2,46}
129: {2,14} 377: {6,10} 623: {4,24}
133: {4,8} 393: {2,32} 669: {2,48}
159: {2,16} 417: {2,34} 687: {2,50}
183: {2,18} 427: {4,18} 689: {6,16}
203: {4,10} 453: {2,36} 703: {8,12}
213: {2,20} 481: {6,12} 707: {4,26}
237: {2,22} 489: {2,38} 717: {2,52}
247: {6,8} 497: {4,20} 749: {4,28}
259: {4,12} 519: {2,40} 753: {2,54}


MATHEMATICA

Select[Range[100], SquareFreeQ[#]&&PrimeOmega[#]==2&&OddQ[Times@@(1+ PrimePi/@First/@FactorInteger[#])]&]


CROSSREFS

A338911 is the not necessarily squarefree version.
A339003 is the odd instead of even version, with not necessarily squarefree version A338910.
A300912 lists products of pairs of primes with relatively prime indices.
A318990 lists products of pairs of primes with divisible indices.
A320656 counts factorizations into squarefree semiprimes.
A338904 groups semiprimes by weight.
Cf. A000040, A001221, A001222, A056239, A112798, A166237, A195017, A320911, A338901, A338903, A339002.


KEYWORD

nonn


AUTHOR



STATUS

approved



