A227306 Numbers k that divide sigma(k) + sigma(k-1).

2, 6, 34, 50, 216, 236, 262, 386, 898, 924, 945, 1456, 2380, 5356, 6468, 6624, 8362, 14100, 23496, 26938, 46594, 80876, 196344, 212796, 1661136, 4070200, 4160920, 4626700, 5244548, 5462384, 17062316, 60464628, 217408416, 248621604, 262792908, 265371336, 323987588

Offset

1,1

Comments

Is 945 the only odd term? - Zak Seidov, Jul 06 2013

945 and 19910536425 are the only odd terms below 2^36. - Alex Ratushnyak, Jul 08 2013

The third odd term is a(58) = 841488503841. - Giovanni Resta, Apr 04 2014

Links

Giovanni Resta, Table of n, a(n) for n = 1..65 (terms < 10^13)

Mathematica

With[{nn=324*10^6}, Select[Thread[{Total/@Partition[DivisorSigma[ 1, Range[ nn]], 2, 1], Range[ 2, nn]}], Divisible[#[[1]], #[[2]]]&][[All, 2]]] (* Harvey P. Dale, May 29 2020 *)

Crossrefs

Cf. A000203, A092403, A007691, A068078, A186103, A072188.

Sequence in context: A088125 A064940 A105142 * A192537 A026966 A026976

Adjacent sequences: A227303 A227304 A227305 * A227307 A227308 A227309

Keyword

nonn

Author

Alex Ratushnyak, Jul 05 2013

Status

approved