A224901 Least positive integer k such that k*sigma(n) forms an increasing sequence.

1, 1, 1, 1, 2, 2, 4, 3, 4, 3, 5, 3, 7, 5, 6, 5, 9, 5, 10, 5, 7, 7, 11, 5, 10, 8, 9, 7, 14, 6, 14, 8, 11, 10, 12, 7, 17, 11, 12, 8, 18, 8, 18, 10, 11, 12, 19, 8, 18, 12, 16, 12, 22, 10, 17, 11, 17, 16, 25, 9, 25, 17, 16, 14, 22, 13, 28, 16, 22, 15, 31, 12, 32, 21, 20, 18, 27, 16, 34, 15, 24

Offset

1,5

Links

Paul D. Hanna, Table of n, a(n) for n = 1..10000

Example

 The product a(n)*sigma(n) forms an increasing sequence that begins:
[1, 3, 4, 7, 12, 24, 32, 45, 52, 54, 60, 84, 98, 120, 144, 155, 162, 195, ...].

Prog

(PARI) a(n)=if(n==1, 1, (a(n-1)*sigma(n-1))\sigma(n)+1)
for(n=1, 80, print1(a(n), ", "))

Crossrefs

Sequence in context: A074747 A128248 A347659 * A366651 A274176 A356148

Adjacent sequences: A224898 A224899 A224900 * A224902 A224903 A224904

Keyword

nonn

Author

Paul D. Hanna, Aug 16 2013

Status

approved