A067738 - OEIS

A067738

Numbers k such that sigma(k) + sigma(sigma(k)) is prime.

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

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OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[2000], PrimeQ[DivisorSigma[1, #]+DivisorSigma[1, DivisorSigma[ 1, #]]]&] (* Harvey P. Dale, Apr 02 2018 *)

CROSSREFS

Cf. A000203, A023194, A051027.

Sequence in context: A001532 A109456 A155745 * A296287 A187014 A053966

Adjacent sequences: A067735 A067736 A067737 * A067739 A067740 A067741

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Feb 23 2002

STATUS

approved