login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069143 a(1) = a(2) = 1; a(n) = sigma(a(n-1)+a(n-2)). 0
1, 1, 3, 7, 18, 31, 57, 180, 320, 1092, 2478, 10368, 25704, 100800, 393120, 1965600, 10326624, 39657600, 131580288, 511223790, 1469266560, 4911616440, 22120488000, 95841111600, 460020244320, 2163425531904, 9805180170240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..27.

MATHEMATICA

a[1] = a[2] = 1; a[n_] := a[n] = DivisorSigma[1, a[n - 1] + a[n - 2]]; Table[a[n], {n, 27}]

RecurrenceTable[{a[1]==a[2]==1, a[n]==DivisorSigma[1, a[n-1]+a[n-2]]}, a, {n, 30}] (* Harvey P. Dale, Feb 15 2015 *)

CROSSREFS

Sequence in context: A102329 A331713 A327321 * A097007 A308445 A328653

Adjacent sequences:  A069140 A069141 A069142 * A069144 A069145 A069146

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Apr 08 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Apr 11 2002

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 27 13:45 EDT 2021. Contains 348276 sequences. (Running on oeis4.)