A054005 Sum of divisors of k such that k and k+1 have the same number and sum of divisors.

24, 2160, 2640, 4320, 51840, 65280, 115200, 138240, 194400, 186048, 276480, 483840, 622080, 700416, 950400, 984960, 1118880, 1128960, 1612800, 2661120, 3937248, 3617280, 5019840, 6128640, 5806080, 7375680, 8467200, 11583936

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..1831

Formula

a(n) = sigma(A054004(n)).

Example

See example in A054004.

Mathematica

Select[Partition[Table[{n, DivisorSigma[0, n], DivisorSigma[1, n]}, {n, 116*10^5}], 2, 1], #[[1, 2]]== #[[2, 2]] && #[[1, 3]]==#[[2, 3]]&][[All, 1, 3]] (* Harvey P. Dale, May 16 2023 *)

Crossrefs

Cf. A000005, A000203, A002961, A005237, A053249, A054004, A054006, A054007.

Sequence in context: A194472 A246602 A001501 * A107675 A173115 A202927

Adjacent sequences: A054002 A054003 A054004 * A054006 A054007 A054008

Keyword

nonn

Author

Asher Auel, Jan 12 2000

Extensions

More terms from Jud McCranie, Oct 15 2000

Definition clarified by Harvey P. Dale, May 16 2023

Status

approved