|
Search: id:A108605
|
|
|
| A108605 |
|
Semiprimes with prime sum of factors. |
|
+0
6
|
|
| 6, 10, 22, 34, 58, 82, 118, 142, 202, 214, 274, 298, 358, 382, 394, 454, 478, 538, 562, 622, 694, 838, 862, 922, 1042, 1138, 1198, 1234, 1282, 1318, 1618, 1642, 1654, 1714, 1762, 2038, 2062, 2098, 2122, 2182, 2302, 2458, 2554, 2578, 2602, 2638, 2854, 2902
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
All terms are even.
The definition implies that the sum of factors is the sum over the prime factors with multiplicity, as in A001414. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 28 2008
|
|
FORMULA
|
a(n)=2*p, with p and 2+p twin primes; a(n)=2*A001359(n).
|
|
EXAMPLE
|
58=2*29 and 2+29 is prime.
|
|
MATHEMATICA
|
Select[Range[2, 3000, 2], !IntegerQ[Sqrt[ # ]]&&Plus@@(Transpose[FactorInteger[ # ]])[[2]]==2&&PrimeQ[Plus@@(Transpose[FactorInteger[ # ]])[[1]]]&]
|
|
CROSSREFS
|
Cf. A001358 semiprimes, A001359 lesser of twin primes, A101605 3-almost primes, A108606 semiprimes with prime sum of digits, A108607 intersection of A108605 and A108606.
Sequence in context: A102783 A157037 A082917 this_sequence A063765 A085712 A145351
Adjacent sequences: A108602 A108603 A108604 this_sequence A108606 A108607 A108608
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Zak Seidov (zakseidov(AT)yahoo.com), Jun 12 2005
|
|
EXTENSIONS
|
Changed division by 2 to multiplication by 2 in formula related to A001359. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 28 2008
|
|
|
Search completed in 0.002 seconds
|
