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

Author

Asher Auel, Jan 12 2000

Keywords

• nonn

Examples

			See example in A054004.
		

Links

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

Crossrefs

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

Programs

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 *)

Formula

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

Extensions

More terms from Jud McCranie, Oct 15 2000

Definition clarified by Harvey P. Dale, May 16 2023