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A067738 Numbers k such that sigma(k) + sigma(sigma(k)) is prime. 1
1, 2, 3, 7, 22, 32, 49, 52, 66, 70, 93, 94, 97, 98, 115, 119, 121, 127, 169, 170, 196, 214, 241, 242, 256, 265, 337, 343, 364, 441, 450, 513, 529, 567, 577, 578, 597, 679, 723, 784, 800, 841, 967, 1058, 1225, 1249, 1369, 1444, 1521, 1682, 1731, 1802, 1849 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MATHEMATICA
Select[Range[2000], PrimeQ[DivisorSigma[1, #]+DivisorSigma[1, DivisorSigma[ 1, #]]]&] (* Harvey P. Dale, Apr 02 2018 *)
CROSSREFS
Sequence in context: A001532 A109456 A155745 * A296287 A187014 A053966
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 23 2002
STATUS
approved

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)