login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A324891 a(n) = sigma(A170818(n)), where A170818(n) is the part of n composed of prime factors of form 4k+1. 2
1, 1, 1, 1, 6, 1, 1, 1, 1, 6, 1, 1, 14, 1, 6, 1, 18, 1, 1, 6, 1, 1, 1, 1, 31, 14, 1, 1, 30, 6, 1, 1, 1, 18, 6, 1, 38, 1, 14, 6, 42, 1, 1, 1, 6, 1, 1, 1, 1, 31, 18, 14, 54, 1, 6, 1, 1, 30, 1, 6, 62, 1, 1, 1, 84, 1, 1, 18, 1, 6, 1, 1, 74, 38, 31, 1, 1, 14, 1, 6, 1, 42, 1, 1, 108, 1, 30, 1, 90, 6, 14, 1, 1, 1, 6, 1, 98, 1, 1, 31, 102, 18, 1, 14, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,5
LINKS
FORMULA
Multiplicative with a(p^e) = (p^(e+1) - 1)/(p-1) if p == 1 (mod 4), otherwise a(p^e) = 1.
a(n) = A000203(A170818(n)).
a(n) = A000593(n) / A324893(n).
PROG
(PARI) A324891(n) = { my(f=factor(n)); prod(i=1, #f~, if(f[i, 1]%4>1, 1, ((f[i, 1]^(1+f[i, 2]))-1)/(f[i, 1]-1))); };
(PARI)
A170818(n) = { my(f=factor(n)); prod(i=1, #f~, if(f[i, 1]%4>1, 1, f[i, 1])^f[i, 2]); }; \\ From A170818
A324891(n) = sigma(A170818(n));
CROSSREFS
Sequence in context: A080219 A339747 A293901 * A260340 A040037 A344877
KEYWORD
nonn,mult
AUTHOR
Antti Karttunen, Mar 27 2019
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)