A378659 Positions of records for ratio A003961(n)/sigma(n), where A003961 is fully multiplicative with a(p) = nextprime(p) and sigma is the sum of the divisors function.

1, 3, 4, 7, 8, 9, 16, 27, 32, 64, 128, 243, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864

Offset

1,2

Links

Table of n, a(n) for n=1..31.

Index entries for sequences related to prime indices in the factorization of n

Index entries for sequences related to sigma(n)

Example

  Term k       A003961(k)/A000203(k)    ratio
       1                1/1          =  1
       3                5/4          =  1.25
       4                9/7          =  1.2857143
       7               11/8          =  1.375
       8               27/15         =  1.8
       9               25/13         =  1.9230769
      16               81/31         =  2.6129032
      27              125/40         =  3.125
      32              243/63         =  3.8571429
      64              729/127        =  5.7401575
     128             2187/255        =  8.5764706
     243             3125/364        =  8.5851648
     256             6561/511        =  12.839530
     ...
33554432     847288609443/67108863   =  12625.584
67108864    2541865828329/134217727  =  18938.376

Crossrefs

Cf. A000203, A003961.

Cf. A001359 (apparently gives the positions of successive minima of the ratio, for n > 2).

Cf. also A341529, A349627, A349628, A354827, A354828.

Sequence in context: A363751 A129142 A359749 * A075752 A046541 A324470

Adjacent sequences: A378656 A378657 A378658 * A378660 A378661 A378662

Keyword

nonn

Author

Antti Karttunen, Dec 06 2024

Status

approved