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A114080
Numbers k such that sigma(k) times the k-th prime is a brilliant number (A078972).
0
2, 4, 9, 16, 25, 64, 729, 65536
OFFSET
1,1
COMMENTS
No additional terms up to 1 million. - Harvey P. Dale, Nov 13 2013
EXAMPLE
sigma(25) * p(25) = 3007 = 31*97.
MATHEMATICA
brilQ[n_]:=Module[{pf=Transpose[FactorInteger[n]][[1]]}, PrimeOmega[n] == 2&&IntegerLength[First[pf]]==IntegerLength[Last[pf]]]; Select[Range[ 100000], brilQ[DivisorSigma[1, #]Prime[#]]&] (* Harvey P. Dale, Nov 13 2013 *)
CROSSREFS
Sequence in context: A364131 A077137 A023194 * A090676 A333779 A261240
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved