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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: A241817 A181628 A023387 * A129119 A171251 A074980

Adjacent sequences:  A119620 A119621 A119622 * A119624 A119625 A119626

KEYWORD

nonn

AUTHOR

Zak Seidov, Jun 08 2006

STATUS

approved

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Last modified November 23 14:53 EST 2014. Contains 249851 sequences.