|
| |
|
|
A119623
|
|
Composite numbers for which the second elementary symmetric function of divisors (s2) is prime.
|
|
1
|
|
|
|
6, 10, 14, 26, 34, 62, 82, 122, 142, 146, 202, 206, 226, 254, 334, 346, 362, 394, 446, 542, 562, 566, 586, 734, 766, 794, 842, 926, 934, 982, 1046, 1126, 1286, 1294, 1346, 1382, 1514, 1546, 1594, 1622, 1654, 1706, 1766, 1906, 1934
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Terms in A119616 are always prime if n is prime p and s2(p)=p, hence it is interesting to find composite numbers for which s2 is also prime. Relative values of s2 are: s2=47,97,163,457,733,2203,3733,7993,10723,11317,21313,22147,26557,33403,57283,61417,67153,79393,101467,149323,160453,162727,174337,272683,296827,318793,358273,432907,440383,486583,551767,639007,832687,843043,911917,961183,1152913,1202017,1277593,1322743,1375303,1462897,1567327,1824997,1878883. Otherwise the sequence s2 gives numbers which appear in A119616 at least twice (and conjecture is that exactly twice).
|
|
|
LINKS
|
Table of n, a(n) for n=1..45.
|
|
|
MATHEMATICA
|
dv:=Divisors[n]; le:=Length[dv]; re=Reap[Do[If[ !PrimeQ[n], su=Sum[dv[[i]]*dv[[i+j]], {i, 1, le-1}, {j, 1, le-i}]; If[PrimeQ[su], Sow[{n, su}]]], {n, 2, 2000}]][[2, 1]]
|
|
|
CROSSREFS
|
Cf. A119616.
Sequence in context: A207574 A181628 A023387 * A129119 A171251 A074980
Adjacent sequences: A119620 A119621 A119622 * A119624 A119625 A119626
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Zak Seidov, Jun 08 2006
|
|
|
STATUS
|
approved
|
| |
|
|
